media: ov7740: Document device tree bindings

Add the device tree binding documentation for the ov7740 sensor driver.
Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/devicetree/bindings/media/i2c/ov7740.txt

+* Omnivision OV7740 CMOS image sensor
+
+The Omnivision OV7740 image sensor supports multiple output image
+size, such as VGA, and QVGA, CIF and any size smaller. It also
+supports the RAW RGB and YUV output formats.
+
+The common video interfaces bindings (see video-interfaces.txt) should
+be used to specify link to the image data receiver. The OV7740 device
+node should contain one 'port' child node with an 'endpoint' subnode.
+
+Required Properties:
+- compatible:	"ovti,ov7740".
+- reg:		I2C slave address of the sensor.
+- clocks:	Reference to the xvclk input clock.
+- clock-names:	"xvclk".
+
+Optional Properties:
+- reset-gpios: Rreference to the GPIO connected to the reset_b pin,
+  if any. Active low with pull-ip resistor.
+- powerdown-gpios: Reference to the GPIO connected to the pwdn pin,
+  if any. Active high with pull-down resistor.
+
+Endpoint node mandatory properties:
+- remote-endpoint: A phandle to the bus receiver's endpoint node.
+
+Example:
+
+	i2c1: i2c@fc028000 {
+		ov7740: camera@21 {
+			compatible = "ovti,ov7740";
+			reg = <0x21>;
+			pinctrl-names = "default";
+			pinctrl-0 = <&pinctrl_sensor_power &pinctrl_sensor_reset>;
+			clocks = <&isc>;
+			clock-names = "xvclk";
+			assigned-clocks = <&isc>;
+			assigned-clock-rates = <24000000>;
+			reset-gpios = <&pioA 43 GPIO_ACTIVE_LOW>;
+			powerdown-gpios = <&pioA 44 GPIO_ACTIVE_HIGH>;
+
+			port {
+				ov7740_0: endpoint {
+					remote-endpoint = <&isc_0>;
+				};
+			};
+		};
+	};