dt-bindings: Add devicetree bindings to devicetree project

  Devicetree (DT) ABI

I. Regarding stable bindings/ABI, we quote from the 2013 ARM mini-summit

   summary document:

     "That still leaves the question of, what does a stable binding look

     like?  Certainly a stable binding means that a newer kernel will not

     break on an older device tree, but that doesn't mean the binding is

     frozen for all time. Grant said there are ways to change bindings that

     don't result in breakage. For instance, if a new property is added,

     then default to the previous behaviour if it is missing. If a binding

     truly needs an incompatible change, then change the compatible string

     at the same time.  The driver can bind against both the old and the

     new. These guidelines aren't new, but they desperately need to be

     documented."

II.  General binding rules

  1) Maintainers, don't let perfect be the enemy of good.  Don't hold up a

     binding because it isn't perfect.

  2) Use specific compatible strings so that if we need to add a feature (DMA)

     in the future, we can create a new compatible string.  See I.

  3) Bindings can be augmented, but the driver shouldn't break when given

     the old binding. ie. add additional properties, but don't change the

     meaning of an existing property. For drivers, default to the original

     behaviour when a newly added property is missing.

  4) Don't submit bindings for staging or unstable.  That will be decided by

     the devicetree maintainers *after* discussion on the mailinglist.

III. Notes

  1) This document is intended as a general familiarization with the process as

     decided at the 2013 Kernel Summit.  When in doubt, the current word of the

     devicetree maintainers overrules this document.  In that situation, a patch

     updating this document would be appreciated.

* ARC HS Performance Counters

The ARC HS can be configured with a pipeline performance monitor for counting

CPU and cache events like cache misses and hits. Like conventional PCT there

are 100+ hardware conditions dynamically mapped to up to 32 counters.

It also supports overflow interrupts.

Required properties:

- compatible : should contain

	"snps,archs-pct"

Example:

pmu {

        compatible = "snps,archs-pct";

};

Synopsys DesignWare ARC Software Development Platforms Device Tree Bindings

---------------------------------------------------------------------------

SDP Main Board with an AXC001 CPU Card hoisting ARC700 core in silicon

Required root node properties:

    - compatible = "snps,axs101", "snps,arc-sdp";

Synopsys DesignWare ARC Software Development Platforms Device Tree Bindings

---------------------------------------------------------------------------

SDP Main Board with an AXC003 FPGA Card which can contain various flavours of

HS38x cores.

Required root node properties:

    - compatible = "snps,axs103", "snps,arc-sdp";

EZchip NPS Network Processor Platforms Device Tree Bindings

---------------------------------------------------------------------------

Appliance main board with NPS400 ASIC.

Required root node properties:

    - compatible = "ezchip,arc-nps";