dt-bindings: EXYNOS: Add exynos-srom device tree binding

SAMSUNG Exynos SoCs SROM Controller driver.

Required properties:

- compatible : Should contain "samsung,exynos4210-srom".

- reg: offset and length of the register set

Optional properties:

The SROM controller can be used to attach external peripherals. In this case

extra properties, describing the bus behind it, should be specified as below:

- #address-cells: Must be set to 2 to allow device address translation.

		  Address is specified as (bank#, offset).

- #size-cells: Must be set to 1 to allow device size passing

- ranges: Must be set up to reflect the memory layout with four integer values

	  per bank:

		<bank-number> 0 <parent address of bank> <size>

Sub-nodes:

The actual device nodes should be added as subnodes to the SROMc node. These

subnodes, in addition to regular device specification, should contain the following

properties, describing configuration of the relevant SROM bank:

Required properties:

- reg: bank number, base address (relative to start of the bank) and size of

       the memory mapped for the device. Note that base address will be

       typically 0 as this is the start of the bank.

- samsung,srom-timing : array of 6 integers, specifying bank timings in the

                        following order: Tacp, Tcah, Tcoh, Tacc, Tcos, Tacs.

                        Each value is specified in cycles and has the following

                        meaning and valid range:

                        Tacp : Page mode access cycle at Page mode (0 - 15)

                        Tcah : Address holding time after CSn (0 - 15)

                        Tcoh : Chip selection hold on OEn (0 - 15)

                        Tacc : Access cycle (0 - 31, the actual time is N + 1)

                        Tcos : Chip selection set-up before OEn (0 - 15)

                        Tacs : Address set-up before CSn (0 - 15)

Optional properties:

- reg-io-width : data width in bytes (1 or 2). If omitted, default of 1 is used.

- samsung,srom-page-mode : if page mode is set, 4 data page mode will be configured,

			   else normal (1 data) page mode will be set.

Example: basic definition, no banks are configured

	memory-controller@12570000 {

		compatible = "samsung,exynos4210-srom";

		reg = <0x12570000 0x14>;

	};

Example: SROMc with SMSC911x ethernet chip on bank 3

	memory-controller@12570000 {

		#address-cells = <2>;

		#size-cells = <1>;

		ranges = <0 0 0x04000000 0x20000   // Bank0

			  1 0 0x05000000 0x20000   // Bank1

			  2 0 0x06000000 0x20000   // Bank2

			  3 0 0x07000000 0x20000>; // Bank3

		compatible = "samsung,exynos4210-srom";

		reg = <0x12570000 0x14>;

		ethernet@3,0 {

			compatible = "smsc,lan9115";

			reg = <3 0 0x10000>;	   // Bank 3, offset = 0

			phy-mode = "mii";

			interrupt-parent = <&gpx0>;

			interrupts = <5 8>;

			reg-io-width = <2>;

			smsc,irq-push-pull;

			smsc,force-internal-phy;

			samsung,srom-page-mode;

			samsung,srom-timing = <9 12 1 9 1 1>;

		};

	};