ON Semiconductor NCP6335d regulator

NCP6335d is able to deliver up to 5.0 A, with programmable output voltage from
0.6 V to 1.87 V in 10mV steps, with synchronous rectification and automatic PWM/
PFM transitions, enable pins and power good/fail signaling.

The NCP6335d interface is via I2C bus.

Required Properties:
- compatible:			Must be "onnn,ncp6335d-regulator".
- reg:				The device 8-bit I2C address.
- regulator-min-microvolt:	Minimum voltage in microvolts supported by this
				regulator.
- regulator-max-microvolt:	Maximum voltage in microvolts supported by this
				regulator.
- onnn,min-setpoint:		Minimum setpoint voltage in microvolts supported
				by this regulator.
- onnn,step-size:		The step size of the regulator, in uV.
- onnn,min-slew-ns:		Minimum time in ns needed to change voltage by
				one step size. This value corresponds to DVS
				mode bit of 00b in command register.
- onnn,max-slew-ns:		Maximum time in ns needed to change voltage by
				one step size. This value corresponds to DVS
				mode bit of 11b in command register.
- onnn,vsel:			Working vsel register. Supported value are 0
				or 1.
- onnn,slew-ns:			Time in ns needed to change voltage by one step
				size. Supported value are 333, 666, 1333, 2666.

Optional Properties:
- onnn,discharge-enable:	Present: discharge enabled.
				Not Present: discharge disabled.
- onnn,restore-reg:		Present: Restore vsel register from backup register.
				Not Present: No restore.
- onnn,vsel-gpio:		Present: GPIO connects to the VSEL pin and set the
				VSEL pin according to device tree flag.
				Not Present: No GPIO is connected to vsel pin.
- pinctrl-names:		The state name of the VSEL pin configuration.
				Only support: "default"
- pinctrl-0:			The phandles of the pin configuration node in
				pinctrl for VSEL pin.
				For details of pinctrl properties, please refer to:
				"Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt"
- onnn,sleep-enable:		Present: Forced in sleep mode when EN and VSEL
				pins are low.
				Not Present: Low quiescent current mode when EN and VSEL
				pins are low.
- onnn,mode:			A string which specifies the initial mode to use for the regulator.
				Supported values are "pwm" and "auto". PWM mode is more
				robust, but draws more current than auto mode. If this propery
				is not specified, then the regulator will be in the hardware default mode.

Example:
	i2c_0 {
		ncp6335d-regulator@1c {
			compatible = "onnn,ncp6335d-regulator";
			reg = <0x1c>;
			onnn,vsel = <0>;
			onnn,slew-rate-ns = <2666>;
			onnn,discharge-enable;
			onnn,step-size = <10000>;
			onnn,min-slew-ns = <333>;
			onnn,max-slew-ns = <2666>;
			pintrl-names = "default";
			pinctrl-0 = <&ext_buck_vsel_default>;

			regulator-min-microvolt = <1050000>;
			regulator-max-microvolt = <1350000>;
			onnn,min-setpoint = <600000>;
			onnn,vsel-gpio = <&msmgpio 2 1>;
		};
	};