dt-bindings: mux-adg792a: document devicetree bindings for ADG792A/G mux

Bindings for Analog Devices ADG792A/G Triple 4:1 Multiplexers

Required properties:

- compatible : "adi,adg792a" or "adi,adg792g"

- #mux-control-cells : <0> if parallel (the three muxes are bound together

  with a single mux controller controlling all three muxes), or <1> if

  not (one mux controller for each mux).

* Standard mux-controller bindings as described in mux-controller.txt

Optional properties for ADG792G:

- gpio-controller : if present, #gpio-cells below is required.

- #gpio-cells : should be <2>

			  - First cell is the GPO line number, i.e. 0 or 1

			  - Second cell is used to specify active high (0)

			    or active low (1)

Optional properties:

- idle-state : if present, array of states that the mux controllers will have

  when idle. The special state MUX_IDLE_AS_IS is the default and

  MUX_IDLE_DISCONNECT is also supported.

States 0 through 3 correspond to signals A through D in the datasheet.

Example:

	/*

	 * Three independent mux controllers (of which one is used).

	 * Mux 0 is disconnected when idle, mux 1 idles in the previously

	 * selected state and mux 2 idles with signal B.

	 */

	&i2c0 {

		mux: mux-controller@50 {

			compatible = "adi,adg792a";

			reg = <0x50>;

			#mux-control-cells = <1>;

			idle-state = <MUX_IDLE_DISCONNECT MUX_IDLE_AS_IS 1>;

		};

	};

	adc-mux {

		compatible = "io-channel-mux";

		io-channels = <&adc 0>;

		io-channel-names = "parent";

		mux-controls = <&mux 2>;

		channels = "sync-1", "", "out";

	};

	/*

	 * Three parallel muxes with one mux controller, useful e.g. if

	 * the adc is differential, thus needing two signals to be muxed

	 * simultaneously for correct operation.

	 */

	&i2c0 {

		pmux: mux-controller@50 {

			compatible = "adi,adg792a";

			reg = <0x50>;

			#mux-control-cells = <0>;

			idle-state = <1>;

		};

	};

	diff-adc-mux {

		compatible = "io-channel-mux";

		io-channels = <&adc 0>;

		io-channel-names = "parent";

		mux-controls = <&pmux>;

		channels = "sync-1", "", "out";

	};