Regulator of AMS AS3722 PMIC.
Name of the regulator subnode must be "regulators".

Optional properties:
--------------------
The input supply of regulators are the optional properties on the
regulator node. The AS3722 is having 7 DCDC step-down regulators as
sd[0-6], 10 LDOs as ldo[0-7], ldo[9-11]. The input supply of these
regulators are provided through following properties:
vsup-sd2-supply: Input supply for SD2.
vsup-sd3-supply: Input supply for SD3.
vsup-sd4-supply: Input supply for SD4.
vsup-sd5-supply: Input supply for SD5.
vin-ldo0-supply: Input supply for LDO0.
vin-ldo1-6-supply: Input supply for LDO1 and LDO6.
vin-ldo2-5-7-supply: Input supply for LDO2, LDO5 and LDO7.
vin-ldo3-4-supply: Input supply for LDO3 and LDO4.
vin-ldo9-10-supply: Input supply for LDO9 and LDO10.
vin-ldo11-supply: Input supply for LDO11.

Optional nodes:
--------------
- regulators : Must contain a sub-node per regulator from the list below.
	       Each sub-node should contain the constraints and initialization
	       information for that regulator. See regulator.txt for a
	       description of standard properties for these sub-nodes.
	       Additional custom properties  are listed below.
	       sd[0-6], ldo[0-7], ldo[9-11].

	       Optional sub-node properties:
	       ----------------------------
		ams,ext-control: External control of the rail. The option of
			this properties will tell which external input is
			controlling this rail. Valid values are 0, 1, 2 ad 3.
			0: There is no external control of this rail.
			1: Rail is controlled by ENABLE1 input pin.
			2: Rail is controlled by ENABLE2 input pin.
			3: Rail is controlled by ENABLE3 input pin.
		ams,enable-tracking: Enable tracking with SD1, only supported
			by LDO3.

Example:
-------
	ams3722: ams3722 {
		compatible = "ams,as3722";
		reg = <0x40>;
		...

		regulators {
			vsup-sd2-supply = <...>;
			...

			sd0 {
				regulator-name = "vdd_cpu";
				regulator-min-microvolt = <700000>;
				regulator-max-microvolt = <1400000>;
				regulator-always-on;
				ams,ext-control = <2>;
			};

			sd1 {
				regulator-name = "vdd_core";
				regulator-min-microvolt = <700000>;
				regulator-max-microvolt = <1400000>;
				regulator-always-on;
				ams,ext-control = <1>;
			};

			sd2 {
				regulator-name = "vddio_ddr";
				regulator-min-microvolt = <1350000>;
				regulator-max-microvolt = <1350000>;
				regulator-always-on;
			};

			sd4 {
				regulator-name = "avdd-hdmi-pex";
				regulator-min-microvolt = <1050000>;
				regulator-max-microvolt = <1050000>;
				regulator-always-on;
			};

			sd5 {
				regulator-name = "vdd-1v8";
				regulator-min-microvolt = <1800000>;
				regulator-max-microvolt = <1800000>;
				regulator-always-on;
			};
			....
		};
	};