* OmniVision ov4688 MIPI sensor

Required Properties:
- compatible: should be "ovti,ov4688"
- clocks: reference to the 24M xvclk input clock.
- clock-names: should be "xvclk".
- dovdd-supply: Digital I/O voltage supply, 1.8 volts
- avdd-supply: Analog voltage supply, 2.8 volts
- dvdd-supply: Digital core voltage supply, 1.2 volts
- reset-gpios: Low active reset gpio

Attention:
SC4238 device address 0x36(7bit);

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:
//rv1126 evb13 board
&i2c1 {
	status = "okay";
	ov4688: ov4688@36 {
		compatible = "smartsens,ov4688";
		reg = <0x36>;
		clocks = <&cru CLK_MIPICSI_OUT>;
		clock-names = "xvclk";
		power-domains = <&power RV1126_PD_VI>;
		pinctrl-names = "rockchip,camera_default";
		pinctrl-0 = <&mipicsi_clk0>;
		avdd-supply = <&vcc_avdd>;
		dovdd-supply = <&vcc_dovdd>;
		dvdd-supply = <&vcc_dvdd>;
		pwdn-gpios = <&gpio1 RK_PD4 GPIO_ACTIVE_HIGH>;
		reset-gpios = <&gpio1 RK_PD5 GPIO_ACTIVE_LOW>;
		rockchip,camera-module-index = <1>;
		rockchip,camera-module-facing = "front";
		rockchip,camera-module-name = "ODF1981";
		rockchip,camera-module-lens-name = "40IRC-4M-F18";
		/* NO_HDR:0 HDR_X2:5 HDR_X3:6 */
		rockchip,camera-hdr-mode = <0>;
		ir-cut = <&cam_ircut0>;
		port {
			sc4238_out: endpoint {
				remote-endpoint = <&mipi_in_ucam1>;
				data-lanes = <1 2 3 4>;
			};
		};
	};
};