Doc/DT: Add DT binding documentation for TFP410 encoder

Add DT binding documentation for TFP410 encoder
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Archit Taneja <archit@ti.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/video/ti,tfp410.txt

+TFP410 DPI to DVI encoder
+=========================
+
+Required properties:
+- compatible: "ti,tfp410"
+
+Optional properties:
+- powerdown-gpios: power-down gpio
+
+Required nodes:
+- Video port 0 for DPI input
+- Video port 1 for DVI output
+
+Example
+-------
+
+tfp410: encoder@0 {
+	compatible = "ti,tfp410";
+	powerdown-gpios = <&twl_gpio 2 GPIO_ACTIVE_LOW>;
+
+	ports {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		port@0 {
+			reg = <0>;
+
+			tfp410_in: endpoint@0 {
+				remote-endpoint = <&dpi_out>;
+			};
+		};
+
+		port@1 {
+			reg = <1>;
+
+			tfp410_out: endpoint@0 {
+				remote-endpoint = <&dvi_connector_in>;
+			};
+		};
+	};
+};