Toshiba TC358767 eDP bridge bindings

Required properties:
 - compatible: "toshiba,tc358767"
 - reg: i2c address of the bridge, 0x68 or 0x0f, depending on bootstrap pins
 - clock-names: should be "ref"
 - clocks: OF device-tree clock specification for refclk input. The reference
   clock rate must be 13 MHz, 19.2 MHz, 26 MHz, or 38.4 MHz.

Optional properties:
 - shutdown-gpios: OF device-tree gpio specification for SD pin
                   (active high shutdown input)
 - reset-gpios: OF device-tree gpio specification for RSTX pin
                (active low system reset)
 - toshiba,hpd-pin: TC358767 GPIO pin number to which HPD is connected to (0 or 1)
 - ports: the ports node can contain video interface port nodes to connect
   to a DPI/DSI source and to an eDP/DP sink according to [1][2]:
    - port@0: DSI input port
    - port@1: DPI input port
    - port@2: eDP/DP output port

[1]: Documentation/devicetree/bindings/graph.txt
[2]: Documentation/devicetree/bindings/media/video-interfaces.txt

Example:
	edp-bridge@68 {
		compatible = "toshiba,tc358767";
		reg = <0x68>;
		shutdown-gpios = <&gpio3 23 GPIO_ACTIVE_HIGH>;
		reset-gpios = <&gpio3 24 GPIO_ACTIVE_LOW>;
		clock-names = "ref";
		clocks = <&edp_refclk>;

		ports {
			#address-cells = <1>;
			#size-cells = <0>;

			port@1 {
				reg = <1>;

				bridge_in: endpoint {
					remote-endpoint = <&dpi_out>;
				};
			};

			port@2 {
				reg = <2>;

				bridge_out: endpoint {
					remote-endpoint = <&panel_in>;
				};
			};
		};
	};