MediaTek MT6397/MT6323 Multifunction Device Driver

MT6397/MT6323 is a multifunction device with the following sub modules:
- Regulator
- RTC
- Audio codec
- GPIO
- Clock
- LED
- Keys

It is interfaced to host controller using SPI interface by a proprietary hardware
called PMIC wrapper or pwrap. MT6397/MT6323 MFD is a child device of pwrap.
See the following for pwarp node definitions:
Documentation/devicetree/bindings/soc/mediatek/pwrap.txt

This document describes the binding for MFD device and its sub module.

Required properties:
compatible: "mediatek,mt6397" or "mediatek,mt6323"

Optional subnodes:

- rtc
	Required properties:
		- compatible: "mediatek,mt6397-rtc"
- regulators
	Required properties:
		- compatible: "mediatek,mt6397-regulator"
	see Documentation/devicetree/bindings/regulator/mt6397-regulator.txt
		- compatible: "mediatek,mt6323-regulator"
	see Documentation/devicetree/bindings/regulator/mt6323-regulator.txt
- codec
	Required properties:
		- compatible: "mediatek,mt6397-codec"
- clk
	Required properties:
		- compatible: "mediatek,mt6397-clk"
- led
	Required properties:
		- compatible: "mediatek,mt6323-led"
	see Documentation/devicetree/bindings/leds/leds-mt6323.txt

- keys
	Required properties:
		- compatible: "mediatek,mt6397-keys" or "mediatek,mt6323-keys"
	see Documentation/devicetree/bindings/input/mtk-pmic-keys.txt

Example:
	pwrap: pwrap@1000f000 {
		compatible = "mediatek,mt8135-pwrap";

		...

		pmic {
			compatible = "mediatek,mt6397";

			codec: mt6397codec {
				compatible = "mediatek,mt6397-codec";
			};

			regulators {
				compatible = "mediatek,mt6397-regulator";

				mt6397_vpca15_reg: buck_vpca15 {
					regulator-compatible = "buck_vpca15";
					regulator-name = "vpca15";
					regulator-min-microvolt = <850000>;
					regulator-max-microvolt = <1400000>;
					regulator-ramp-delay = <12500>;
					regulator-always-on;
				};

				mt6397_vgp4_reg: ldo_vgp4 {
					regulator-compatible = "ldo_vgp4";
					regulator-name = "vgp4";
					regulator-min-microvolt = <1200000>;
					regulator-max-microvolt = <3300000>;
					regulator-enable-ramp-delay = <218>;
				};
			};
		};
	};