dt-bindings: mmc: add DT binding for S3C24XX MMC/SD/SDIO controller

* Samsung's S3C24XX MMC/SD/SDIO controller device tree bindings

Samsung's S3C24XX MMC/SD/SDIO controller is used as a connectivity interface

with external MMC, SD and SDIO storage mediums.

This file documents differences between the core mmc properties described by

mmc.txt and the properties used by the Samsung S3C24XX MMC/SD/SDIO controller

implementation.

Required SoC Specific Properties:

- compatible: should be one of the following

  - "samsung,s3c2410-sdi": for controllers compatible with s3c2410

  - "samsung,s3c2412-sdi": for controllers compatible with s3c2412

  - "samsung,s3c2440-sdi": for controllers compatible with s3c2440

- reg: register location and length

- interrupts: mmc controller interrupt

- clocks: Should reference the controller clock

- clock-names: Should contain "sdi"

Required Board Specific Properties:

- pinctrl-0: Should specify pin control groups used for this controller.

- pinctrl-names: Should contain only one value - "default".

Optional Properties:

- bus-width: number of data lines (see mmc.txt)

- cd-gpios: gpio for card detection (see mmc.txt)

- wp-gpios: gpio for write protection (see mmc.txt)

Example:

	mmc0: mmc@5a000000 {

		compatible = "samsung,s3c2440-sdi";

		pinctrl-names = "default";

		pinctrl-0 = <&sdi_pins>;

		reg = <0x5a000000 0x100000>;

		interrupts = <0 0 21 3>;

		clocks = <&clocks PCLK_SDI>;

		clock-names = "sdi";

		bus-width = <4>;

		cd-gpios = <&gpg 8 GPIO_ACTIVE_LOW>;

		wp-gpios = <&gph 8 GPIO_ACTIVE_LOW>;

	};