Doc/DT: Add DT binding documentation for Analog TV Connector

Add DT binding documentation for Analog TV Connector.
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/analog-tv-connector.txt

+Analog TV Connector
+===================
+
+Required properties:
+- compatible: "composite-connector" or "svideo-connector"
+
+Optional properties:
+- label: a symbolic name for the connector
+
+Required nodes:
+- Video port for TV input
+
+Example
+-------
+
+tv: connector {
+	compatible = "composite-connector";
+	label = "tv";
+
+	port {
+		tv_connector_in: endpoint {
+			remote-endpoint = <&venc_out>;
+		};
+	};
+};