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+           Booting the Linux/ppc kernel without Open Firmware
+           --------------------------------------------------
+
+(c) 2005 Benjamin Herrenschmidt <benh at kernel.crashing.org>,
+    IBM Corp.
+(c) 2005 Becky Bruce <becky.bruce at freescale.com>,
+    Freescale Semiconductor, FSL SOC and 32-bit additions
+(c) 2006 MontaVista Software, Inc.
+    Flash chip node definition
+
+Table of Contents
+=================
+
+  I - Introduction
+    1) Entry point for arch/arm
+    2) Entry point for arch/powerpc
+    3) Entry point for arch/x86
+    4) Entry point for arch/mips/bmips
+
+  II - The DT block format
+    1) Header
+    2) Device tree generalities
+    3) Device tree "structure" block
+    4) Device tree "strings" block
+
+  III - Required content of the device tree
+    1) Note about cells and address representation
+    2) Note about "compatible" properties
+    3) Note about "name" properties
+    4) Note about node and property names and character set
+    5) Required nodes and properties
+      a) The root node
+      b) The /cpus node
+      c) The /cpus/* nodes
+      d) the /memory node(s)
+      e) The /chosen node
+      f) the /soc<SOCname> node
+
+  IV - "dtc", the device tree compiler
+
+  V - Recommendations for a bootloader
+
+  VI - System-on-a-chip devices and nodes
+    1) Defining child nodes of an SOC
+    2) Representing devices without a current OF specification
+
+  VII - Specifying interrupt information for devices
+    1) interrupts property
+    2) interrupt-parent property
+    3) OpenPIC Interrupt Controllers
+    4) ISA Interrupt Controllers
+
+  VIII - Specifying device power management information (sleep property)
+
+  IX - Specifying dma bus information
+
+  Appendix A - Sample SOC node for MPC8540
+
+
+Revision Information
+====================
+
+   May 18, 2005: Rev 0.1 - Initial draft, no chapter III yet.
+
+   May 19, 2005: Rev 0.2 - Add chapter III and bits & pieces here or
+                           clarifies the fact that a lot of things are
+                           optional, the kernel only requires a very
+                           small device tree, though it is encouraged
+                           to provide an as complete one as possible.
+
+   May 24, 2005: Rev 0.3 - Precise that DT block has to be in RAM
+			 - Misc fixes
+			 - Define version 3 and new format version 16
+			   for the DT block (version 16 needs kernel
+			   patches, will be fwd separately).
+			   String block now has a size, and full path
+			   is replaced by unit name for more
+			   compactness.
+			   linux,phandle is made optional, only nodes
+			   that are referenced by other nodes need it.
+			   "name" property is now automatically
+			   deduced from the unit name
+
+   June 1, 2005: Rev 0.4 - Correct confusion between OF_DT_END and
+                           OF_DT_END_NODE in structure definition.
+                         - Change version 16 format to always align
+                           property data to 4 bytes. Since tokens are
+                           already aligned, that means no specific
+                           required alignment between property size
+                           and property data. The old style variable
+                           alignment would make it impossible to do
+                           "simple" insertion of properties using
+                           memmove (thanks Milton for
+                           noticing). Updated kernel patch as well
+			 - Correct a few more alignment constraints
+			 - Add a chapter about the device-tree
+                           compiler and the textural representation of
+                           the tree that can be "compiled" by dtc.
+
+   November 21, 2005: Rev 0.5
+			 - Additions/generalizations for 32-bit
+			 - Changed to reflect the new arch/powerpc
+			   structure
+			 - Added chapter VI
+
+
+ ToDo:
+	- Add some definitions of interrupt tree (simple/complex)
+	- Add some definitions for PCI host bridges
+	- Add some common address format examples
+	- Add definitions for standard properties and "compatible"
+	  names for cells that are not already defined by the existing
+	  OF spec.
+	- Compare FSL SOC use of PCI to standard and make sure no new
+	  node definition required.
+	- Add more information about node definitions for SOC devices
+  	  that currently have no standard, like the FSL CPM.
+
+
+I - Introduction
+================
+
+During the development of the Linux/ppc64 kernel, and more
+specifically, the addition of new platform types outside of the old
+IBM pSeries/iSeries pair, it was decided to enforce some strict rules
+regarding the kernel entry and bootloader <-> kernel interfaces, in
+order to avoid the degeneration that had become the ppc32 kernel entry
+point and the way a new platform should be added to the kernel. The
+legacy iSeries platform breaks those rules as it predates this scheme,
+but no new board support will be accepted in the main tree that
+doesn't follow them properly.  In addition, since the advent of the
+arch/powerpc merged architecture for ppc32 and ppc64, new 32-bit
+platforms and 32-bit platforms which move into arch/powerpc will be
+required to use these rules as well.
+
+The main requirement that will be defined in more detail below is
+the presence of a device-tree whose format is defined after Open
+Firmware specification. However, in order to make life easier
+to embedded board vendors, the kernel doesn't require the device-tree
+to represent every device in the system and only requires some nodes
+and properties to be present. This will be described in detail in
+section III, but, for example, the kernel does not require you to
+create a node for every PCI device in the system. It is a requirement
+to have a node for PCI host bridges in order to provide interrupt
+routing information and memory/IO ranges, among others. It is also
+recommended to define nodes for on chip devices and other buses that
+don't specifically fit in an existing OF specification. This creates a
+great flexibility in the way the kernel can then probe those and match
+drivers to device, without having to hard code all sorts of tables. It
+also makes it more flexible for board vendors to do minor hardware
+upgrades without significantly impacting the kernel code or cluttering
+it with special cases.
+
+
+1) Entry point for arch/arm
+---------------------------
+
+   There is one single entry point to the kernel, at the start
+   of the kernel image. That entry point supports two calling
+   conventions.  A summary of the interface is described here.  A full
+   description of the boot requirements is documented in
+   Documentation/arm/Booting
+
+        a) ATAGS interface.  Minimal information is passed from firmware
+        to the kernel with a tagged list of predefined parameters.
+
+                r0 : 0
+
+                r1 : Machine type number
+
+                r2 : Physical address of tagged list in system RAM
+
+        b) Entry with a flattened device-tree block.  Firmware loads the
+        physical address of the flattened device tree block (dtb) into r2,
+        r1 is not used, but it is considered good practice to use a valid
+        machine number as described in Documentation/arm/Booting.
+
+                r0 : 0
+
+                r1 : Valid machine type number.  When using a device tree,
+                a single machine type number will often be assigned to
+                represent a class or family of SoCs.
+
+                r2 : physical pointer to the device-tree block
+                (defined in chapter II) in RAM.  Device tree can be located
+                anywhere in system RAM, but it should be aligned on a 64 bit
+                boundary.
+
+   The kernel will differentiate between ATAGS and device tree booting by
+   reading the memory pointed to by r2 and looking for either the flattened
+   device tree block magic value (0xd00dfeed) or the ATAG_CORE value at
+   offset 0x4 from r2 (0x54410001).
+
+2) Entry point for arch/powerpc
+-------------------------------
+
+   There is one single entry point to the kernel, at the start
+   of the kernel image. That entry point supports two calling
+   conventions:
+
+        a) Boot from Open Firmware. If your firmware is compatible
+        with Open Firmware (IEEE 1275) or provides an OF compatible
+        client interface API (support for "interpret" callback of
+        forth words isn't required), you can enter the kernel with:
+
+              r5 : OF callback pointer as defined by IEEE 1275
+              bindings to powerpc. Only the 32-bit client interface
+              is currently supported
+
+              r3, r4 : address & length of an initrd if any or 0
+
+              The MMU is either on or off; the kernel will run the
+              trampoline located in arch/powerpc/kernel/prom_init.c to
+              extract the device-tree and other information from open
+              firmware and build a flattened device-tree as described
+              in b). prom_init() will then re-enter the kernel using
+              the second method. This trampoline code runs in the
+              context of the firmware, which is supposed to handle all
+              exceptions during that time.
+
+        b) Direct entry with a flattened device-tree block. This entry
+        point is called by a) after the OF trampoline and can also be
+        called directly by a bootloader that does not support the Open
+        Firmware client interface. It is also used by "kexec" to
+        implement "hot" booting of a new kernel from a previous
+        running one. This method is what I will describe in more
+        details in this document, as method a) is simply standard Open
+        Firmware, and thus should be implemented according to the
+        various standard documents defining it and its binding to the
+        PowerPC platform. The entry point definition then becomes:
+
+                r3 : physical pointer to the device-tree block
+                (defined in chapter II) in RAM
+
+                r4 : physical pointer to the kernel itself. This is
+                used by the assembly code to properly disable the MMU
+                in case you are entering the kernel with MMU enabled
+                and a non-1:1 mapping.
+
+                r5 : NULL (as to differentiate with method a)
+
+        Note about SMP entry: Either your firmware puts your other
+        CPUs in some sleep loop or spin loop in ROM where you can get
+        them out via a soft reset or some other means, in which case
+        you don't need to care, or you'll have to enter the kernel
+        with all CPUs. The way to do that with method b) will be
+        described in a later revision of this document.
+
+   Board supports (platforms) are not exclusive config options. An
+   arbitrary set of board supports can be built in a single kernel
+   image. The kernel will "know" what set of functions to use for a
+   given platform based on the content of the device-tree. Thus, you
+   should:
+
+        a) add your platform support as a _boolean_ option in
+        arch/powerpc/Kconfig, following the example of PPC_PSERIES,
+        PPC_PMAC and PPC_MAPLE. The later is probably a good
+        example of a board support to start from.
+
+        b) create your main platform file as
+        "arch/powerpc/platforms/myplatform/myboard_setup.c" and add it
+        to the Makefile under the condition of your CONFIG_
+        option. This file will define a structure of type "ppc_md"
+        containing the various callbacks that the generic code will
+        use to get to your platform specific code
+
+  A kernel image may support multiple platforms, but only if the
+  platforms feature the same core architecture.  A single kernel build
+  cannot support both configurations with Book E and configurations
+  with classic Powerpc architectures.
+
+3) Entry point for arch/x86
+-------------------------------
+
+  There is one single 32bit entry point to the kernel at code32_start,
+  the decompressor (the real mode entry point goes to the same  32bit
+  entry point once it switched into protected mode). That entry point
+  supports one calling convention which is documented in
+  Documentation/x86/boot.txt
+  The physical pointer to the device-tree block (defined in chapter II)
+  is passed via setup_data which requires at least boot protocol 2.09.
+  The type filed is defined as
+
+  #define SETUP_DTB                      2
+
+  This device-tree is used as an extension to the "boot page". As such it
+  does not parse / consider data which is already covered by the boot
+  page. This includes memory size, reserved ranges, command line arguments
+  or initrd address. It simply holds information which can not be retrieved
+  otherwise like interrupt routing or a list of devices behind an I2C bus.
+
+4) Entry point for arch/mips/bmips
+----------------------------------
+
+  Some bootloaders only support a single entry point, at the start of the
+  kernel image.  Other bootloaders will jump to the ELF start address.
+  Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y,
+  so the first instruction immediately jumps to kernel_entry().
+
+  Similar to the arch/arm case (b), a DT-aware bootloader is expected to
+  set up the following registers:
+
+         a0 : 0
+
+         a1 : 0xffffffff
+
+         a2 : Physical pointer to the device tree block (defined in chapter
+         II) in RAM.  The device tree can be located anywhere in the first
+         512MB of the physical address space (0x00000000 - 0x1fffffff),
+         aligned on a 64 bit boundary.
+
+  Legacy bootloaders do not use this convention, and they do not pass in a
+  DT block.  In this case, Linux will look for a builtin DTB, selected via
+  CONFIG_DT_*.
+
+  This convention is defined for 32-bit systems only, as there are not
+  currently any 64-bit BMIPS implementations.
+
+II - The DT block format
+========================
+
+
+This chapter defines the actual format of the flattened device-tree
+passed to the kernel. The actual content of it and kernel requirements
+are described later. You can find example of code manipulating that
+format in various places, including arch/powerpc/kernel/prom_init.c
+which will generate a flattened device-tree from the Open Firmware
+representation, or the fs2dt utility which is part of the kexec tools
+which will generate one from a filesystem representation. It is
+expected that a bootloader like uboot provides a bit more support,
+that will be discussed later as well.
+
+Note: The block has to be in main memory. It has to be accessible in
+both real mode and virtual mode with no mapping other than main
+memory. If you are writing a simple flash bootloader, it should copy
+the block to RAM before passing it to the kernel.
+
+
+1) Header
+---------
+
+   The kernel is passed the physical address pointing to an area of memory
+   that is roughly described in include/linux/of_fdt.h by the structure
+   boot_param_header:
+
+struct boot_param_header {
+        u32     magic;                  /* magic word OF_DT_HEADER */
+        u32     totalsize;              /* total size of DT block */
+        u32     off_dt_struct;          /* offset to structure */
+        u32     off_dt_strings;         /* offset to strings */
+        u32     off_mem_rsvmap;         /* offset to memory reserve map
+                                           */
+        u32     version;                /* format version */
+        u32     last_comp_version;      /* last compatible version */
+
+        /* version 2 fields below */
+        u32     boot_cpuid_phys;        /* Which physical CPU id we're
+                                           booting on */
+        /* version 3 fields below */
+        u32     size_dt_strings;        /* size of the strings block */
+
+        /* version 17 fields below */
+        u32	size_dt_struct;		/* size of the DT structure block */
+};
+
+   Along with the constants:
+
+/* Definitions used by the flattened device tree */
+#define OF_DT_HEADER            0xd00dfeed      /* 4: version,
+						   4: total size */
+#define OF_DT_BEGIN_NODE        0x1             /* Start node: full name
+						   */
+#define OF_DT_END_NODE          0x2             /* End node */
+#define OF_DT_PROP              0x3             /* Property: name off,
+                                                   size, content */
+#define OF_DT_END               0x9
+
+   All values in this header are in big endian format, the various
+   fields in this header are defined more precisely below. All
+   "offset" values are in bytes from the start of the header; that is
+   from the physical base address of the device tree block.
+
+   - magic
+
+     This is a magic value that "marks" the beginning of the
+     device-tree block header. It contains the value 0xd00dfeed and is
+     defined by the constant OF_DT_HEADER
+
+   - totalsize
+
+     This is the total size of the DT block including the header. The
+     "DT" block should enclose all data structures defined in this
+     chapter (who are pointed to by offsets in this header). That is,
+     the device-tree structure, strings, and the memory reserve map.
+
+   - off_dt_struct
+
+     This is an offset from the beginning of the header to the start
+     of the "structure" part the device tree. (see 2) device tree)
+
+   - off_dt_strings
+
+     This is an offset from the beginning of the header to the start
+     of the "strings" part of the device-tree
+
+   - off_mem_rsvmap
+
+     This is an offset from the beginning of the header to the start
+     of the reserved memory map. This map is a list of pairs of 64-
+     bit integers. Each pair is a physical address and a size. The
+     list is terminated by an entry of size 0. This map provides the
+     kernel with a list of physical memory areas that are "reserved"
+     and thus not to be used for memory allocations, especially during
+     early initialization. The kernel needs to allocate memory during
+     boot for things like un-flattening the device-tree, allocating an
+     MMU hash table, etc... Those allocations must be done in such a
+     way to avoid overriding critical things like, on Open Firmware
+     capable machines, the RTAS instance, or on some pSeries, the TCE
+     tables used for the iommu. Typically, the reserve map should
+     contain _at least_ this DT block itself (header,total_size). If
+     you are passing an initrd to the kernel, you should reserve it as
+     well. You do not need to reserve the kernel image itself. The map
+     should be 64-bit aligned.
+
+   - version
+
+     This is the version of this structure. Version 1 stops
+     here. Version 2 adds an additional field boot_cpuid_phys.
+     Version 3 adds the size of the strings block, allowing the kernel
+     to reallocate it easily at boot and free up the unused flattened
+     structure after expansion. Version 16 introduces a new more
+     "compact" format for the tree itself that is however not backward
+     compatible. Version 17 adds an additional field, size_dt_struct,
+     allowing it to be reallocated or moved more easily (this is
+     particularly useful for bootloaders which need to make
+     adjustments to a device tree based on probed information). You
+     should always generate a structure of the highest version defined
+     at the time of your implementation. Currently that is version 17,
+     unless you explicitly aim at being backward compatible.
+
+   - last_comp_version
+
+     Last compatible version. This indicates down to what version of
+     the DT block you are backward compatible. For example, version 2
+     is backward compatible with version 1 (that is, a kernel build
+     for version 1 will be able to boot with a version 2 format). You
+     should put a 1 in this field if you generate a device tree of
+     version 1 to 3, or 16 if you generate a tree of version 16 or 17
+     using the new unit name format.
+
+   - boot_cpuid_phys
+
+     This field only exist on version 2 headers. It indicate which
+     physical CPU ID is calling the kernel entry point. This is used,
+     among others, by kexec. If you are on an SMP system, this value
+     should match the content of the "reg" property of the CPU node in
+     the device-tree corresponding to the CPU calling the kernel entry
+     point (see further chapters for more information on the required
+     device-tree contents)
+
+   - size_dt_strings
+
+     This field only exists on version 3 and later headers.  It
+     gives the size of the "strings" section of the device tree (which
+     starts at the offset given by off_dt_strings).
+
+   - size_dt_struct
+
+     This field only exists on version 17 and later headers.  It gives
+     the size of the "structure" section of the device tree (which
+     starts at the offset given by off_dt_struct).
+
+   So the typical layout of a DT block (though the various parts don't
+   need to be in that order) looks like this (addresses go from top to
+   bottom):
+
+
+             ------------------------------
+     base -> |  struct boot_param_header  |
+             ------------------------------
+             |      (alignment gap) (*)   |
+             ------------------------------
+             |      memory reserve map    |
+             ------------------------------
+             |      (alignment gap)       |
+             ------------------------------
+             |                            |
+             |    device-tree structure   |
+             |                            |
+             ------------------------------
+             |      (alignment gap)       |
+             ------------------------------
+             |                            |
+             |     device-tree strings    |
+             |                            |
+      -----> ------------------------------
+      |
+      |
+      --- (base + totalsize)
+
+  (*) The alignment gaps are not necessarily present; their presence
+      and size are dependent on the various alignment requirements of
+      the individual data blocks.
+
+
+2) Device tree generalities
+---------------------------
+
+This device-tree itself is separated in two different blocks, a
+structure block and a strings block. Both need to be aligned to a 4
+byte boundary.
+
+First, let's quickly describe the device-tree concept before detailing
+the storage format. This chapter does _not_ describe the detail of the
+required types of nodes & properties for the kernel, this is done
+later in chapter III.
+
+The device-tree layout is strongly inherited from the definition of
+the Open Firmware IEEE 1275 device-tree. It's basically a tree of
+nodes, each node having two or more named properties. A property can
+have a value or not.
+
+It is a tree, so each node has one and only one parent except for the
+root node who has no parent.
+
+A node has 2 names. The actual node name is generally contained in a
+property of type "name" in the node property list whose value is a
+zero terminated string and is mandatory for version 1 to 3 of the
+format definition (as it is in Open Firmware). Version 16 makes it
+optional as it can generate it from the unit name defined below.
+
+There is also a "unit name" that is used to differentiate nodes with
+the same name at the same level, it is usually made of the node
+names, the "@" sign, and a "unit address", which definition is
+specific to the bus type the node sits on.
+
+The unit name doesn't exist as a property per-se but is included in
+the device-tree structure. It is typically used to represent "path" in
+the device-tree. More details about the actual format of these will be
+below.
+
+The kernel generic code does not make any formal use of the
+unit address (though some board support code may do) so the only real
+requirement here for the unit address is to ensure uniqueness of
+the node unit name at a given level of the tree. Nodes with no notion
+of address and no possible sibling of the same name (like /memory or
+/cpus) may omit the unit address in the context of this specification,
+or use the "@0" default unit address. The unit name is used to define
+a node "full path", which is the concatenation of all parent node
+unit names separated with "/".
+
+The root node doesn't have a defined name, and isn't required to have
+a name property either if you are using version 3 or earlier of the
+format. It also has no unit address (no @ symbol followed by a unit
+address). The root node unit name is thus an empty string. The full
+path to the root node is "/".
+
+Every node which actually represents an actual device (that is, a node
+which isn't only a virtual "container" for more nodes, like "/cpus"
+is) is also required to have a "compatible" property indicating the
+specific hardware and an optional list of devices it is fully
+backwards compatible with.
+
+Finally, every node that can be referenced from a property in another
+node is required to have either a "phandle" or a "linux,phandle"
+property. Real Open Firmware implementations provide a unique
+"phandle" value for every node that the "prom_init()" trampoline code
+turns into "linux,phandle" properties. However, this is made optional
+if the flattened device tree is used directly. An example of a node
+referencing another node via "phandle" is when laying out the
+interrupt tree which will be described in a further version of this
+document.
+
+The "phandle" property is a 32-bit value that uniquely
+identifies a node. You are free to use whatever values or system of
+values, internal pointers, or whatever to generate these, the only
+requirement is that every node for which you provide that property has
+a unique value for it.
+
+Here is an example of a simple device-tree. In this example, an "o"
+designates a node followed by the node unit name. Properties are
+presented with their name followed by their content. "content"
+represents an ASCII string (zero terminated) value, while <content>
+represents a 32-bit value, specified in decimal or hexadecimal (the
+latter prefixed 0x). The various nodes in this example will be
+discussed in a later chapter. At this point, it is only meant to give
+you a idea of what a device-tree looks like. I have purposefully kept
+the "name" and "linux,phandle" properties which aren't necessary in
+order to give you a better idea of what the tree looks like in
+practice.
+
+  / o device-tree
+      |- name = "device-tree"
+      |- model = "MyBoardName"
+      |- compatible = "MyBoardFamilyName"
+      |- #address-cells = <2>
+      |- #size-cells = <2>
+      |- linux,phandle = <0>
+      |
+      o cpus
+      | | - name = "cpus"
+      | | - linux,phandle = <1>
+      | | - #address-cells = <1>
+      | | - #size-cells = <0>
+      | |
+      | o PowerPC,970@0
+      |   |- name = "PowerPC,970"
+      |   |- device_type = "cpu"
+      |   |- reg = <0>
+      |   |- clock-frequency = <0x5f5e1000>
+      |   |- 64-bit
+      |   |- linux,phandle = <2>
+      |
+      o memory@0
+      | |- name = "memory"
+      | |- device_type = "memory"
+      | |- reg = <0x00000000 0x00000000 0x00000000 0x20000000>
+      | |- linux,phandle = <3>
+      |
+      o chosen
+        |- name = "chosen"
+        |- bootargs = "root=/dev/sda2"
+        |- linux,phandle = <4>
+
+This tree is almost a minimal tree. It pretty much contains the
+minimal set of required nodes and properties to boot a linux kernel;
+that is, some basic model information at the root, the CPUs, and the
+physical memory layout.  It also includes misc information passed
+through /chosen, like in this example, the platform type (mandatory)
+and the kernel command line arguments (optional).
+
+The /cpus/PowerPC,970@0/64-bit property is an example of a
+property without a value. All other properties have a value. The
+significance of the #address-cells and #size-cells properties will be
+explained in chapter IV which defines precisely the required nodes and
+properties and their content.
+
+
+3) Device tree "structure" block
+
+The structure of the device tree is a linearized tree structure. The
+"OF_DT_BEGIN_NODE" token starts a new node, and the "OF_DT_END_NODE"
+ends that node definition. Child nodes are simply defined before
+"OF_DT_END_NODE" (that is nodes within the node). A 'token' is a 32
+bit value. The tree has to be "finished" with a OF_DT_END token
+
+Here's the basic structure of a single node:
+
+     * token OF_DT_BEGIN_NODE (that is 0x00000001)
+     * for version 1 to 3, this is the node full path as a zero
+       terminated string, starting with "/". For version 16 and later,
+       this is the node unit name only (or an empty string for the
+       root node)
+     * [align gap to next 4 bytes boundary]
+     * for each property:
+        * token OF_DT_PROP (that is 0x00000003)
+        * 32-bit value of property value size in bytes (or 0 if no
+          value)
+        * 32-bit value of offset in string block of property name
+        * property value data if any
+        * [align gap to next 4 bytes boundary]
+     * [child nodes if any]
+     * token OF_DT_END_NODE (that is 0x00000002)
+
+So the node content can be summarized as a start token, a full path,
+a list of properties, a list of child nodes, and an end token. Every
+child node is a full node structure itself as defined above.
+
+NOTE: The above definition requires that all property definitions for
+a particular node MUST precede any subnode definitions for that node.
+Although the structure would not be ambiguous if properties and
+subnodes were intermingled, the kernel parser requires that the
+properties come first (up until at least 2.6.22).  Any tools
+manipulating a flattened tree must take care to preserve this
+constraint.
+
+4) Device tree "strings" block
+
+In order to save space, property names, which are generally redundant,
+are stored separately in the "strings" block. This block is simply the
+whole bunch of zero terminated strings for all property names
+concatenated together. The device-tree property definitions in the
+structure block will contain offset values from the beginning of the
+strings block.
+
+
+III - Required content of the device tree
+=========================================
+
+WARNING: All "linux,*" properties defined in this document apply only
+to a flattened device-tree. If your platform uses a real
+implementation of Open Firmware or an implementation compatible with
+the Open Firmware client interface, those properties will be created
+by the trampoline code in the kernel's prom_init() file. For example,
+that's where you'll have to add code to detect your board model and
+set the platform number. However, when using the flattened device-tree
+entry point, there is no prom_init() pass, and thus you have to
+provide those properties yourself.
+
+
+1) Note about cells and address representation
+----------------------------------------------
+
+The general rule is documented in the various Open Firmware
+documentations. If you choose to describe a bus with the device-tree
+and there exist an OF bus binding, then you should follow the
+specification. However, the kernel does not require every single
+device or bus to be described by the device tree.
+
+In general, the format of an address for a device is defined by the
+parent bus type, based on the #address-cells and #size-cells
+properties.  Note that the parent's parent definitions of #address-cells
+and #size-cells are not inherited so every node with children must specify
+them.  The kernel requires the root node to have those properties defining
+addresses format for devices directly mapped on the processor bus.
+
+Those 2 properties define 'cells' for representing an address and a
+size. A "cell" is a 32-bit number. For example, if both contain 2
+like the example tree given above, then an address and a size are both
+composed of 2 cells, and each is a 64-bit number (cells are
+concatenated and expected to be in big endian format). Another example
+is the way Apple firmware defines them, with 2 cells for an address
+and one cell for a size.  Most 32-bit implementations should define
+#address-cells and #size-cells to 1, which represents a 32-bit value.
+Some 32-bit processors allow for physical addresses greater than 32
+bits; these processors should define #address-cells as 2.
+
+"reg" properties are always a tuple of the type "address size" where
+the number of cells of address and size is specified by the bus
+#address-cells and #size-cells. When a bus supports various address
+spaces and other flags relative to a given address allocation (like
+prefetchable, etc...) those flags are usually added to the top level
+bits of the physical address. For example, a PCI physical address is
+made of 3 cells, the bottom two containing the actual address itself
+while the top cell contains address space indication, flags, and pci
+bus & device numbers.
+
+For buses that support dynamic allocation, it's the accepted practice
+to then not provide the address in "reg" (keep it 0) though while
+providing a flag indicating the address is dynamically allocated, and
+then, to provide a separate "assigned-addresses" property that
+contains the fully allocated addresses. See the PCI OF bindings for
+details.
+
+In general, a simple bus with no address space bits and no dynamic
+allocation is preferred if it reflects your hardware, as the existing
+kernel address parsing functions will work out of the box. If you
+define a bus type with a more complex address format, including things
+like address space bits, you'll have to add a bus translator to the
+prom_parse.c file of the recent kernels for your bus type.
+
+The "reg" property only defines addresses and sizes (if #size-cells is
+non-0) within a given bus. In order to translate addresses upward
+(that is into parent bus addresses, and possibly into CPU physical
+addresses), all buses must contain a "ranges" property. If the
+"ranges" property is missing at a given level, it's assumed that
+translation isn't possible, i.e., the registers are not visible on the
+parent bus.  The format of the "ranges" property for a bus is a list
+of:
+
+	bus address, parent bus address, size
+
+"bus address" is in the format of the bus this bus node is defining,
+that is, for a PCI bridge, it would be a PCI address. Thus, (bus
+address, size) defines a range of addresses for child devices. "parent
+bus address" is in the format of the parent bus of this bus. For
+example, for a PCI host controller, that would be a CPU address. For a
+PCI<->ISA bridge, that would be a PCI address. It defines the base
+address in the parent bus where the beginning of that range is mapped.
+
+For new 64-bit board support, I recommend either the 2/2 format or
+Apple's 2/1 format which is slightly more compact since sizes usually
+fit in a single 32-bit word.   New 32-bit board support should use a
+1/1 format, unless the processor supports physical addresses greater
+than 32-bits, in which case a 2/1 format is recommended.
+
+Alternatively, the "ranges" property may be empty, indicating that the
+registers are visible on the parent bus using an identity mapping
+translation.  In other words, the parent bus address space is the same
+as the child bus address space.
+
+2) Note about "compatible" properties
+-------------------------------------
+
+These properties are optional, but recommended in devices and the root
+node. The format of a "compatible" property is a list of concatenated
+zero terminated strings. They allow a device to express its
+compatibility with a family of similar devices, in some cases,
+allowing a single driver to match against several devices regardless
+of their actual names.
+
+3) Note about "name" properties
+-------------------------------
+
+While earlier users of Open Firmware like OldWorld macintoshes tended
+to use the actual device name for the "name" property, it's nowadays
+considered a good practice to use a name that is closer to the device
+class (often equal to device_type). For example, nowadays, Ethernet
+controllers are named "ethernet", an additional "model" property
+defining precisely the chip type/model, and "compatible" property
+defining the family in case a single driver can driver more than one
+of these chips. However, the kernel doesn't generally put any
+restriction on the "name" property; it is simply considered good
+practice to follow the standard and its evolutions as closely as
+possible.
+
+Note also that the new format version 16 makes the "name" property
+optional. If it's absent for a node, then the node's unit name is then
+used to reconstruct the name. That is, the part of the unit name
+before the "@" sign is used (or the entire unit name if no "@" sign
+is present).
+
+4) Note about node and property names and character set
+-------------------------------------------------------
+
+While Open Firmware provides more flexible usage of 8859-1, this
+specification enforces more strict rules. Nodes and properties should
+be comprised only of ASCII characters 'a' to 'z', '0' to
+'9', ',', '.', '_', '+', '#', '?', and '-'. Node names additionally
+allow uppercase characters 'A' to 'Z' (property names should be
+lowercase. The fact that vendors like Apple don't respect this rule is
+irrelevant here). Additionally, node and property names should always
+begin with a character in the range 'a' to 'z' (or 'A' to 'Z' for node
+names).
+
+The maximum number of characters for both nodes and property names
+is 31. In the case of node names, this is only the leftmost part of
+a unit name (the pure "name" property), it doesn't include the unit
+address which can extend beyond that limit.
+
+
+5) Required nodes and properties
+--------------------------------
+  These are all that are currently required. However, it is strongly
+  recommended that you expose PCI host bridges as documented in the
+  PCI binding to Open Firmware, and your interrupt tree as documented
+  in OF interrupt tree specification.
+
+  a) The root node
+
+  The root node requires some properties to be present:
+
+    - model : this is your board name/model
+    - #address-cells : address representation for "root" devices
+    - #size-cells: the size representation for "root" devices
+    - compatible : the board "family" generally finds its way here,
+      for example, if you have 2 board models with a similar layout,
+      that typically get driven by the same platform code in the
+      kernel, you would specify the exact board model in the
+      compatible property followed by an entry that represents the SoC
+      model.
+
+  The root node is also generally where you add additional properties
+  specific to your board like the serial number if any, that sort of
+  thing. It is recommended that if you add any "custom" property whose
+  name may clash with standard defined ones, you prefix them with your
+  vendor name and a comma.
+
+  b) The /cpus node
+
+  This node is the parent of all individual CPU nodes. It doesn't
+  have any specific requirements, though it's generally good practice
+  to have at least:
+
+               #address-cells = <00000001>
+               #size-cells    = <00000000>
+
+  This defines that the "address" for a CPU is a single cell, and has
+  no meaningful size. This is not necessary but the kernel will assume
+  that format when reading the "reg" properties of a CPU node, see
+  below
+
+  c) The /cpus/* nodes
+
+  So under /cpus, you are supposed to create a node for every CPU on
+  the machine. There is no specific restriction on the name of the
+  CPU, though it's common to call it <architecture>,<core>. For
+  example, Apple uses PowerPC,G5 while IBM uses PowerPC,970FX.
+  However, the Generic Names convention suggests that it would be
+  better to simply use 'cpu' for each cpu node and use the compatible
+  property to identify the specific cpu core.
+
+  Required properties:
+
+    - device_type : has to be "cpu"
+    - reg : This is the physical CPU number, it's a single 32-bit cell
+      and is also used as-is as the unit number for constructing the
+      unit name in the full path. For example, with 2 CPUs, you would
+      have the full path:
+        /cpus/PowerPC,970FX@0
+        /cpus/PowerPC,970FX@1
+      (unit addresses do not require leading zeroes)
+    - d-cache-block-size : one cell, L1 data cache block size in bytes (*)
+    - i-cache-block-size : one cell, L1 instruction cache block size in
+      bytes
+    - d-cache-size : one cell, size of L1 data cache in bytes
+    - i-cache-size : one cell, size of L1 instruction cache in bytes
+
+(*) The cache "block" size is the size on which the cache management
+instructions operate. Historically, this document used the cache
+"line" size here which is incorrect. The kernel will prefer the cache
+block size and will fallback to cache line size for backward
+compatibility.
+
+  Recommended properties:
+
+    - timebase-frequency : a cell indicating the frequency of the
+      timebase in Hz. This is not directly used by the generic code,
+      but you are welcome to copy/paste the pSeries code for setting
+      the kernel timebase/decrementer calibration based on this
+      value.
+    - clock-frequency : a cell indicating the CPU core clock frequency
+      in Hz. A new property will be defined for 64-bit values, but if
+      your frequency is < 4Ghz, one cell is enough. Here as well as
+      for the above, the common code doesn't use that property, but
+      you are welcome to re-use the pSeries or Maple one. A future
+      kernel version might provide a common function for this.
+    - d-cache-line-size : one cell, L1 data cache line size in bytes
+      if different from the block size
+    - i-cache-line-size : one cell, L1 instruction cache line size in
+      bytes if different from the block size
+
+  You are welcome to add any property you find relevant to your board,
+  like some information about the mechanism used to soft-reset the
+  CPUs. For example, Apple puts the GPIO number for CPU soft reset
+  lines in there as a "soft-reset" property since they start secondary
+  CPUs by soft-resetting them.
+
+
+  d) the /memory node(s)
+
+  To define the physical memory layout of your board, you should
+  create one or more memory node(s). You can either create a single
+  node with all memory ranges in its reg property, or you can create
+  several nodes, as you wish. The unit address (@ part) used for the
+  full path is the address of the first range of memory defined by a
+  given node. If you use a single memory node, this will typically be
+  @0.
+
+  Required properties:
+
+    - device_type : has to be "memory"
+    - reg : This property contains all the physical memory ranges of
+      your board. It's a list of addresses/sizes concatenated
+      together, with the number of cells of each defined by the
+      #address-cells and #size-cells of the root node. For example,
+      with both of these properties being 2 like in the example given
+      earlier, a 970 based machine with 6Gb of RAM could typically
+      have a "reg" property here that looks like:
+
+      00000000 00000000 00000000 80000000
+      00000001 00000000 00000001 00000000
+
+      That is a range starting at 0 of 0x80000000 bytes and a range
+      starting at 0x100000000 and of 0x100000000 bytes. You can see
+      that there is no memory covering the IO hole between 2Gb and
+      4Gb. Some vendors prefer splitting those ranges into smaller
+      segments, but the kernel doesn't care.
+
+  e) The /chosen node
+
+  This node is a bit "special". Normally, that's where Open Firmware
+  puts some variable environment information, like the arguments, or
+  the default input/output devices.
+
+  This specification makes a few of these mandatory, but also defines
+  some linux-specific properties that would be normally constructed by
+  the prom_init() trampoline when booting with an OF client interface,
+  but that you have to provide yourself when using the flattened format.
+
+  Recommended properties:
+
+    - bootargs : This zero-terminated string is passed as the kernel
+      command line
+    - linux,stdout-path : This is the full path to your standard
+      console device if any. Typically, if you have serial devices on
+      your board, you may want to put the full path to the one set as
+      the default console in the firmware here, for the kernel to pick
+      it up as its own default console.
+
+  Note that u-boot creates and fills in the chosen node for platforms
+  that use it.
+
+  (Note: a practice that is now obsolete was to include a property
+  under /chosen called interrupt-controller which had a phandle value
+  that pointed to the main interrupt controller)
+
+  f) the /soc<SOCname> node
+
+  This node is used to represent a system-on-a-chip (SoC) and must be
+  present if the processor is a SoC. The top-level soc node contains
+  information that is global to all devices on the SoC. The node name
+  should contain a unit address for the SoC, which is the base address
+  of the memory-mapped register set for the SoC. The name of an SoC
+  node should start with "soc", and the remainder of the name should
+  represent the part number for the soc.  For example, the MPC8540's
+  soc node would be called "soc8540".
+
+  Required properties:
+
+    - ranges : Should be defined as specified in 1) to describe the
+      translation of SoC addresses for memory mapped SoC registers.
+    - bus-frequency: Contains the bus frequency for the SoC node.
+      Typically, the value of this field is filled in by the boot
+      loader.
+    - compatible : Exact model of the SoC
+
+
+  Recommended properties:
+
+    - reg : This property defines the address and size of the
+      memory-mapped registers that are used for the SOC node itself.
+      It does not include the child device registers - these will be
+      defined inside each child node.  The address specified in the
+      "reg" property should match the unit address of the SOC node.
+    - #address-cells : Address representation for "soc" devices.  The
+      format of this field may vary depending on whether or not the
+      device registers are memory mapped.  For memory mapped
+      registers, this field represents the number of cells needed to
+      represent the address of the registers.  For SOCs that do not
+      use MMIO, a special address format should be defined that
+      contains enough cells to represent the required information.
+      See 1) above for more details on defining #address-cells.
+    - #size-cells : Size representation for "soc" devices
+    - #interrupt-cells : Defines the width of cells used to represent
+       interrupts.  Typically this value is <2>, which includes a
+       32-bit number that represents the interrupt number, and a
+       32-bit number that represents the interrupt sense and level.
+       This field is only needed if the SOC contains an interrupt
+       controller.
+
+  The SOC node may contain child nodes for each SOC device that the
+  platform uses.  Nodes should not be created for devices which exist
+  on the SOC but are not used by a particular platform. See chapter VI
+  for more information on how to specify devices that are part of a SOC.
+
+  Example SOC node for the MPC8540:
+
+	soc8540@e0000000 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		#interrupt-cells = <2>;
+		device_type = "soc";
+		ranges = <0x00000000 0xe0000000 0x00100000>
+		reg = <0xe0000000 0x00003000>;
+		bus-frequency = <0>;
+	}
+
+
+
+IV - "dtc", the device tree compiler
+====================================
+
+
+dtc source code can be found at
+<http://git.jdl.com/gitweb/?p=dtc.git>
+
+WARNING: This version is still in early development stage; the
+resulting device-tree "blobs" have not yet been validated with the
+kernel. The current generated block lacks a useful reserve map (it will
+be fixed to generate an empty one, it's up to the bootloader to fill
+it up) among others. The error handling needs work, bugs are lurking,
+etc...
+
+dtc basically takes a device-tree in a given format and outputs a
+device-tree in another format. The currently supported formats are:
+
+  Input formats:
+  -------------
+
+     - "dtb": "blob" format, that is a flattened device-tree block
+       with
+        header all in a binary blob.
+     - "dts": "source" format. This is a text file containing a
+       "source" for a device-tree. The format is defined later in this
+        chapter.
+     - "fs" format. This is a representation equivalent to the
+        output of /proc/device-tree, that is nodes are directories and
+	properties are files
+
+ Output formats:
+ ---------------
+
+     - "dtb": "blob" format
+     - "dts": "source" format
+     - "asm": assembly language file. This is a file that can be
+       sourced by gas to generate a device-tree "blob". That file can
+       then simply be added to your Makefile. Additionally, the
+       assembly file exports some symbols that can be used.
+
+
+The syntax of the dtc tool is
+
+    dtc [-I <input-format>] [-O <output-format>]
+        [-o output-filename] [-V output_version] input_filename
+
+
+The "output_version" defines what version of the "blob" format will be
+generated. Supported versions are 1,2,3 and 16. The default is
+currently version 3 but that may change in the future to version 16.
+
+Additionally, dtc performs various sanity checks on the tree, like the
+uniqueness of linux, phandle properties, validity of strings, etc...
+
+The format of the .dts "source" file is "C" like, supports C and C++
+style comments.
+
+/ {
+}
+
+The above is the "device-tree" definition. It's the only statement
+supported currently at the toplevel.
+
+/ {
+  property1 = "string_value";	/* define a property containing a 0
+                                 * terminated string
+				 */
+
+  property2 = <0x1234abcd>;	/* define a property containing a
+                                 * numerical 32-bit value (hexadecimal)
+				 */
+
+  property3 = <0x12345678 0x12345678 0xdeadbeef>;
+                                /* define a property containing 3
+                                 * numerical 32-bit values (cells) in
+                                 * hexadecimal
+				 */
+  property4 = [0x0a 0x0b 0x0c 0x0d 0xde 0xea 0xad 0xbe 0xef];
+                                /* define a property whose content is
+                                 * an arbitrary array of bytes
+                                 */
+
+  childnode@address {	/* define a child node named "childnode"
+                                 * whose unit name is "childnode at
+				 * address"
+                                 */
+
+    childprop = "hello\n";      /* define a property "childprop" of
+                                 * childnode (in this case, a string)
+                                 */
+  };
+};
+
+Nodes can contain other nodes etc... thus defining the hierarchical
+structure of the tree.
+
+Strings support common escape sequences from C: "\n", "\t", "\r",
+"\(octal value)", "\x(hex value)".
+
+It is also suggested that you pipe your source file through cpp (gcc
+preprocessor) so you can use #include's, #define for constants, etc...
+
+Finally, various options are planned but not yet implemented, like
+automatic generation of phandles, labels (exported to the asm file so
+you can point to a property content and change it easily from whatever
+you link the device-tree with), label or path instead of numeric value
+in some cells to "point" to a node (replaced by a phandle at compile
+time), export of reserve map address to the asm file, ability to
+specify reserve map content at compile time, etc...
+
+We may provide a .h include file with common definitions of that
+proves useful for some properties (like building PCI properties or
+interrupt maps) though it may be better to add a notion of struct
+definitions to the compiler...
+
+
+V - Recommendations for a bootloader
+====================================
+
+
+Here are some various ideas/recommendations that have been proposed
+while all this has been defined and implemented.
+
+  - The bootloader may want to be able to use the device-tree itself
+    and may want to manipulate it (to add/edit some properties,
+    like physical memory size or kernel arguments). At this point, 2
+    choices can be made. Either the bootloader works directly on the
+    flattened format, or the bootloader has its own internal tree
+    representation with pointers (similar to the kernel one) and
+    re-flattens the tree when booting the kernel. The former is a bit
+    more difficult to edit/modify, the later requires probably a bit
+    more code to handle the tree structure. Note that the structure
+    format has been designed so it's relatively easy to "insert"
+    properties or nodes or delete them by just memmoving things
+    around. It contains no internal offsets or pointers for this
+    purpose.
+
+  - An example of code for iterating nodes & retrieving properties
+    directly from the flattened tree format can be found in the kernel
+    file drivers/of/fdt.c.  Look at the of_scan_flat_dt() function,
+    its usage in early_init_devtree(), and the corresponding various
+    early_init_dt_scan_*() callbacks. That code can be re-used in a
+    GPL bootloader, and as the author of that code, I would be happy
+    to discuss possible free licensing to any vendor who wishes to
+    integrate all or part of this code into a non-GPL bootloader.
+    (reference needed; who is 'I' here? ---gcl Jan 31, 2011)
+
+
+
+VI - System-on-a-chip devices and nodes
+=======================================
+
+Many companies are now starting to develop system-on-a-chip
+processors, where the processor core (CPU) and many peripheral devices
+exist on a single piece of silicon.  For these SOCs, an SOC node
+should be used that defines child nodes for the devices that make
+up the SOC. While platforms are not required to use this model in
+order to boot the kernel, it is highly encouraged that all SOC
+implementations define as complete a flat-device-tree as possible to
+describe the devices on the SOC.  This will allow for the
+genericization of much of the kernel code.
+
+
+1) Defining child nodes of an SOC
+---------------------------------
+
+Each device that is part of an SOC may have its own node entry inside
+the SOC node.  For each device that is included in the SOC, the unit
+address property represents the address offset for this device's
+memory-mapped registers in the parent's address space.  The parent's
+address space is defined by the "ranges" property in the top-level soc
+node. The "reg" property for each node that exists directly under the
+SOC node should contain the address mapping from the child address space
+to the parent SOC address space and the size of the device's
+memory-mapped register file.
+
+For many devices that may exist inside an SOC, there are predefined
+specifications for the format of the device tree node.  All SOC child
+nodes should follow these specifications, except where noted in this
+document.
+
+See appendix A for an example partial SOC node definition for the
+MPC8540.
+
+
+2) Representing devices without a current OF specification
+----------------------------------------------------------
+
+Currently, there are many devices on SoCs that do not have a standard
+representation defined as part of the Open Firmware specifications,
+mainly because the boards that contain these SoCs are not currently
+booted using Open Firmware.  Binding documentation for new devices
+should be added to the Documentation/devicetree/bindings directory.
+That directory will expand as device tree support is added to more and
+more SoCs.
+
+
+VII - Specifying interrupt information for devices
+===================================================
+
+The device tree represents the buses and devices of a hardware
+system in a form similar to the physical bus topology of the
+hardware.
+
+In addition, a logical 'interrupt tree' exists which represents the
+hierarchy and routing of interrupts in the hardware.
+
+The interrupt tree model is fully described in the
+document "Open Firmware Recommended Practice: Interrupt
+Mapping Version 0.9".  The document is available at:
+<http://www.openfirmware.org/ofwg/practice/>
+
+1) interrupts property
+----------------------
+
+Devices that generate interrupts to a single interrupt controller
+should use the conventional OF representation described in the
+OF interrupt mapping documentation.
+
+Each device which generates interrupts must have an 'interrupt'
+property.  The interrupt property value is an arbitrary number of
+of 'interrupt specifier' values which describe the interrupt or
+interrupts for the device.
+
+The encoding of an interrupt specifier is determined by the
+interrupt domain in which the device is located in the
+interrupt tree.  The root of an interrupt domain specifies in
+its #interrupt-cells property the number of 32-bit cells
+required to encode an interrupt specifier.  See the OF interrupt
+mapping documentation for a detailed description of domains.
+
+For example, the binding for the OpenPIC interrupt controller
+specifies  an #interrupt-cells value of 2 to encode the interrupt
+number and level/sense information. All interrupt children in an
+OpenPIC interrupt domain use 2 cells per interrupt in their interrupts
+property.
+
+The PCI bus binding specifies a #interrupt-cell value of 1 to encode
+which interrupt pin (INTA,INTB,INTC,INTD) is used.
+
+2) interrupt-parent property
+----------------------------
+
+The interrupt-parent property is specified to define an explicit
+link between a device node and its interrupt parent in
+the interrupt tree.  The value of interrupt-parent is the
+phandle of the parent node.
+
+If the interrupt-parent property is not defined for a node, its
+interrupt parent is assumed to be an ancestor in the node's
+_device tree_ hierarchy.
+
+3) OpenPIC Interrupt Controllers
+--------------------------------
+
+OpenPIC interrupt controllers require 2 cells to encode
+interrupt information.  The first cell defines the interrupt
+number.  The second cell defines the sense and level
+information.
+
+Sense and level information should be encoded as follows:
+
+	0 = low to high edge sensitive type enabled
+	1 = active low level sensitive type enabled
+	2 = active high level sensitive type enabled
+	3 = high to low edge sensitive type enabled
+
+4) ISA Interrupt Controllers
+----------------------------
+
+ISA PIC interrupt controllers require 2 cells to encode
+interrupt information.  The first cell defines the interrupt
+number.  The second cell defines the sense and level
+information.
+
+ISA PIC interrupt controllers should adhere to the ISA PIC
+encodings listed below:
+
+	0 =  active low level sensitive type enabled
+	1 =  active high level sensitive type enabled
+	2 =  high to low edge sensitive type enabled
+	3 =  low to high edge sensitive type enabled
+
+VIII - Specifying Device Power Management Information (sleep property)
+===================================================================
+
+Devices on SOCs often have mechanisms for placing devices into low-power
+states that are decoupled from the devices' own register blocks.  Sometimes,
+this information is more complicated than a cell-index property can
+reasonably describe.  Thus, each device controlled in such a manner
+may contain a "sleep" property which describes these connections.
+
+The sleep property consists of one or more sleep resources, each of
+which consists of a phandle to a sleep controller, followed by a
+controller-specific sleep specifier of zero or more cells.
+
+The semantics of what type of low power modes are possible are defined
+by the sleep controller.  Some examples of the types of low power modes
+that may be supported are:
+
+ - Dynamic: The device may be disabled or enabled at any time.
+ - System Suspend: The device may request to be disabled or remain
+   awake during system suspend, but will not be disabled until then.
+ - Permanent: The device is disabled permanently (until the next hard
+   reset).
+
+Some devices may share a clock domain with each other, such that they should
+only be suspended when none of the devices are in use.  Where reasonable,
+such nodes should be placed on a virtual bus, where the bus has the sleep
+property.  If the clock domain is shared among devices that cannot be
+reasonably grouped in this manner, then create a virtual sleep controller
+(similar to an interrupt nexus, except that defining a standardized
+sleep-map should wait until its necessity is demonstrated).
+
+IX - Specifying dma bus information
+
+Some devices may have DMA memory range shifted relatively to the beginning of
+RAM, or even placed outside of kernel RAM. For example, the Keystone 2 SoC
+worked in LPAE mode with 4G memory has:
+- RAM range: [0x8 0000 0000, 0x8 FFFF FFFF]
+- DMA range: [  0x8000 0000,   0xFFFF FFFF]
+and DMA range is aliased into first 2G of RAM in HW.
+
+In such cases, DMA addresses translation should be performed between CPU phys
+and DMA addresses. The "dma-ranges" property is intended to be used
+for describing the configuration of such system in DT.
+
+In addition, each DMA master device on the DMA bus may or may not support
+coherent DMA operations. The "dma-coherent" property is intended to be used
+for identifying devices supported coherent DMA operations in DT.
+
+* DMA Bus master
+Optional property:
+- dma-ranges: <prop-encoded-array> encoded as arbitrary number of triplets of
+	(child-bus-address, parent-bus-address, length). Each triplet specified
+	describes a contiguous DMA address range.
+	The dma-ranges property is used to describe the direct memory access (DMA)
+	structure of a memory-mapped bus whose device tree parent can be accessed
+	from DMA operations originating from the bus. It provides a means of
+	defining a mapping or translation between the physical address space of
+	the bus and the physical address space of the parent of the bus.
+	(for more information see ePAPR specification)
+
+* DMA Bus child
+Optional property:
+- dma-ranges: <empty> value. if present - It means that DMA addresses
+	translation has to be enabled for this device.
+- dma-coherent: Present if dma operations are coherent
+
+Example:
+soc {
+		compatible = "ti,keystone","simple-bus";
+		ranges = <0x0 0x0 0x0 0xc0000000>;
+		dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>;
+
+		[...]
+
+		usb: usb@2680000 {
+			compatible = "ti,keystone-dwc3";
+
+			[...]
+			dma-coherent;
+		};
+};
+
+Appendix A - Sample SOC node for MPC8540
+========================================
+
+	soc@e0000000 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "fsl,mpc8540-ccsr", "simple-bus";
+		device_type = "soc";
+		ranges = <0x00000000 0xe0000000 0x00100000>
+		bus-frequency = <0>;
+		interrupt-parent = <&pic>;
+
+		ethernet@24000 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			device_type = "network";
+			model = "TSEC";
+			compatible = "gianfar", "simple-bus";
+			reg = <0x24000 0x1000>;
+			local-mac-address = [ 0x00 0xE0 0x0C 0x00 0x73 0x00 ];
+			interrupts = <0x29 2 0x30 2 0x34 2>;
+			phy-handle = <&phy0>;
+			sleep = <&pmc 0x00000080>;
+			ranges;
+
+			mdio@24520 {
+				reg = <0x24520 0x20>;
+				compatible = "fsl,gianfar-mdio";
+
+				phy0: ethernet-phy@0 {
+					interrupts = <5 1>;
+					reg = <0>;
+				};
+
+				phy1: ethernet-phy@1 {
+					interrupts = <5 1>;
+					reg = <1>;
+				};
+
+				phy3: ethernet-phy@3 {
+					interrupts = <7 1>;
+					reg = <3>;
+				};
+			};
+		};
+
+		ethernet@25000 {
+			device_type = "network";
+			model = "TSEC";
+			compatible = "gianfar";
+			reg = <0x25000 0x1000>;
+			local-mac-address = [ 0x00 0xE0 0x0C 0x00 0x73 0x01 ];
+			interrupts = <0x13 2 0x14 2 0x18 2>;
+			phy-handle = <&phy1>;
+			sleep = <&pmc 0x00000040>;
+		};
+
+		ethernet@26000 {
+			device_type = "network";
+			model = "FEC";
+			compatible = "gianfar";
+			reg = <0x26000 0x1000>;
+			local-mac-address = [ 0x00 0xE0 0x0C 0x00 0x73 0x02 ];
+			interrupts = <0x41 2>;
+			phy-handle = <&phy3>;
+			sleep = <&pmc 0x00000020>;
+		};
+
+		serial@4500 {
+			#address-cells = <1>;
+			#size-cells = <1>;
+			compatible = "fsl,mpc8540-duart", "simple-bus";
+			sleep = <&pmc 0x00000002>;
+			ranges;
+
+			serial@4500 {
+				device_type = "serial";
+				compatible = "ns16550";
+				reg = <0x4500 0x100>;
+				clock-frequency = <0>;
+				interrupts = <0x42 2>;
+			};
+
+			serial@4600 {
+				device_type = "serial";
+				compatible = "ns16550";
+				reg = <0x4600 0x100>;
+				clock-frequency = <0>;
+				interrupts = <0x42 2>;
+			};
+		};
+
+		pic: pic@40000 {
+			interrupt-controller;
+			#address-cells = <0>;
+			#interrupt-cells = <2>;
+			reg = <0x40000 0x40000>;
+			compatible = "chrp,open-pic";
+			device_type = "open-pic";
+		};
+
+		i2c@3000 {
+			interrupts = <0x43 2>;
+			reg = <0x3000 0x100>;
+			compatible  = "fsl-i2c";
+			dfsrr;
+			sleep = <&pmc 0x00000004>;
+		};
+
+		pmc: power@e0070 {
+			compatible = "fsl,mpc8540-pmc", "fsl,mpc8548-pmc";
+			reg = <0xe0070 0x20>;
+		};
+	};