[media] dt-bindings: Add bindings for video-multiplexer device

Video Multiplexer

=================

Video multiplexers allow to select between multiple input ports. Video received

on the active input port is passed through to the output port. Muxes described

by this binding are controlled by a multiplexer controller that is described by

the bindings in Documentation/devicetree/bindings/mux/mux-controller.txt

Required properties:

- compatible : should be "video-mux"

- mux-controls : mux controller node to use for operating the mux

- #address-cells: should be <1>

- #size-cells: should be <0>

- port@*: at least three port nodes containing endpoints connecting to the

  source and sink devices according to of_graph bindings. The last port is

  the output port, all others are inputs.

Optionally, #address-cells, #size-cells, and port nodes can be grouped under a

ports node as described in Documentation/devicetree/bindings/graph.txt.

Example:

	mux: mux-controller {

		compatible = "gpio-mux";

		#mux-control-cells = <0>;

		mux-gpios = <&gpio1 15 GPIO_ACTIVE_HIGH>;

	};

	video-mux {

		compatible = "video-mux";

		mux-controls = <&mux>;

		#address-cells = <1>;

		#size-cells = <0>;

		port@0 {

			reg = <0>;

			mux_in0: endpoint {

				remote-endpoint = <&video_source0_out>;

			};

		};

		port@1 {

			reg = <1>;

			mux_in1: endpoint {

				remote-endpoint = <&video_source1_out>;

			};

		};

		port@2 {

			reg = <2>;

			mux_out: endpoint {

				remote-endpoint = <&capture_interface_in>;

			};

		};

	};

};