[media] media: ov2640: dt: add the device tree binding document

* Omnivision OV2640 CMOS sensor

The Omnivision OV2640 sensor support multiple resolutions output, such as

CIF, SVGA, UXGA. It also can support YUV422/420, RGB565/555 or raw RGB

output format.

Required Properties:

- compatible: should be "ovti,ov2640"

- clocks: reference to the xvclk input clock.

- clock-names: should be "xvclk".

Optional Properties:

- resetb-gpios: reference to the GPIO connected to the resetb pin, if any.

- pwdn-gpios: reference to the GPIO connected to the pwdn pin, if any.

The device node must contain one 'port' child node for its digital output

video port, in accordance with the video interface bindings defined in

Documentation/devicetree/bindings/media/video-interfaces.txt.

Example:

	i2c1: i2c@f0018000 {

		ov2640: camera@0x30 {

			compatible = "ovti,ov2640";

			reg = <0x30>;

			pinctrl-names = "default";

			pinctrl-0 = <&pinctrl_pck1 &pinctrl_ov2640_pwdn &pinctrl_ov2640_resetb>;

			resetb-gpios = <&pioE 24 GPIO_ACTIVE_LOW>;

			pwdn-gpios = <&pioE 29 GPIO_ACTIVE_HIGH>;

			clocks = <&pck1>;

			clock-names = "xvclk";

			assigned-clocks = <&pck1>;

			assigned-clock-rates = <25000000>;

			port {

				ov2640_0: endpoint {

					remote-endpoint = <&isi_0>;

					bus-width = <8>;

				};

			};

		};

	};