dt-bindings: tc358754: add DT bindings

The patch adds bindings to Toshiba DSI/LVDS bridge TC358764.
Bindings describe power supplies, reset gpio and video interfaces.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Maciej Purski <m.purski@samsung.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180725154644.25412-5-a.hajda@samsung.com

Documentation/devicetree/bindings/display/bridge/toshiba,tc358764.txt

+TC358764 MIPI-DSI to LVDS panel bridge
+
+Required properties:
+  - compatible: "toshiba,tc358764"
+  - reg: the virtual channel number of a DSI peripheral
+  - vddc-supply: core voltage supply, 1.2V
+  - vddio-supply: I/O voltage supply, 1.8V or 3.3V
+  - vddlvds-supply: LVDS1/2 voltage supply, 3.3V
+  - reset-gpios: a GPIO spec for the reset pin
+
+The device node can contain following 'port' child nodes,
+according to the OF graph bindings defined in [1]:
+  0: DSI Input, not required, if the bridge is DSI controlled
+  1: LVDS Output, mandatory
+
+[1]: Documentation/devicetree/bindings/media/video-interfaces.txt
+
+Example:
+
+	bridge@0 {
+		reg = <0>;
+		compatible = "toshiba,tc358764";
+		vddc-supply = <&vcc_1v2_reg>;
+		vddio-supply = <&vcc_1v8_reg>;
+		vddlvds-supply = <&vcc_3v3_reg>;
+		reset-gpios = <&gpd1 6 GPIO_ACTIVE_LOW>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		port@1 {
+			reg = <1>;
+			lvds_ep: endpoint {
+				remote-endpoint = <&panel_ep>;
+			};
+		};
+	};