Device-Tree bindings for Rockchip RK618 MFD driver

Required properties:
 - compatible: value should be one of the following:
   "rockchip,rk618"
 - reg: I2C device address.
 - clocks: phandle to the clkin clock provider
 - clock-names: Must be "clkin"
 - reset-gpios: a GPIO spec for the reset pin

Optional properties:
 - power-supply: regulator to provide the supply voltage
 - enable-gpios: a GPIO spec for the enable pin

Example:

&i2c5 {
	status = "okay";

	rk618: rk618@50 {
		compatible = "rockchip,rk618";
		reg = <0x50>;
		pinctrl-names = "default";
		pinctrl-0 = <&i2s_8ch_mclk>;
		clocks = <&cru SCLK_I2S_8CH_OUT>;
		clock-names = "clkin";
		reset-gpios = <&gpio3 14 GPIO_ACTIVE_LOW>;
	};
};