* Hynix hi556 MIPI CSI-2 sensor

Required Properties:
- compatible: should be "hynix,hi556"
- clocks: reference to the 24M xvclk input clock.
- clock-names: should be "xvclk".
- dovdd-supply: Digital I/O voltage supply, 1.8 or 2.8 volts
- avdd-supply: Analog voltage supply, 2.8 volts
- dvdd-supply: Digital core voltage supply, 1.2 volts
- power-gpios : High active reset gpio
- reset-gpios: High active reset gpio
- pwdn-gpios: High active reset gpio
Optional Properties:
- flash-leds : attached led node
- lens-focus : attached vcm for focus

Attention:
hi556 device address 0x20(7bit) or 0x28(7bit) is decided by I2C_ID_SEL pin;

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:
//RK356x Board
&i2c4 {
	status = "okay";

	hi556: hi556@20 {
		status = "okay";
		compatible = "hynix,hi556";
		reg = <0x20>;
		clocks = <&cru CLK_CIF_OUT>;
		clock-names = "xvclk";
		power-domains = <&power RK3568_PD_VI>;
		pinctrl-names = "default";
		pinctrl-0 = <&cam_clkout0>;
		power-gpios = <&gpio0 RK_PC1 GPIO_ACTIVE_HIGH>;
		reset-gpios = <&gpio4 RK_PA7 GPIO_ACTIVE_HIGH>;
		pwdn-gpios = <&gpio4 RK_PB2 GPIO_ACTIVE_HIGH>;
		rockchip,camera-module-index = <0>;
		rockchip,camera-module-facing = "back";
		rockchip,camera-module-name = "KYT-8607-V1.0";
		rockchip,camera-module-lens-name = "default";
		flash-leds = <&flash_rgb13h>;
		lens-focus = <&dw9714>;
		port {
			hi556_out: endpoint {
				remote-endpoint = <&mipi_in_hi556>;
				data-lanes = <1 2>;
			};
		};
	};
};