regulator: Add document for MediaTek MT6380 regulator

add dt-binding document for MediaTek MT6380 PMIC
Signed-off-by: Chenglin Xu <chenglin.xu@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/mt6380-regulator.txt

+MediaTek MT6380 Regulator
+
+All voltage regulators provided by the MT6380 PMIC are described as the
+subnodes of the MT6380 regulators node. Each regulator is named according
+to its regulator type, buck-<name> and ldo-<name>. The definition for each
+of these nodes is defined using the standard binding for regulators at
+Documentation/devicetree/bindings/regulator/regulator.txt.
+
+The valid names for regulators are:
+BUCK:
+  buck-core1, buck-vcore, buck-vrf
+LDO:
+  ldo-vm ,ldo-va , ldo-vphy, ldo-vddr, ldo-vt
+
+Example:
+
+	regulators {
+		compatible = "mediatek,mt6380-regulator";
+
+		mt6380_vcpu_reg: buck-vcore1 {
+			regulator-name = "vcore1";
+			regulator-min-microvolt = < 600000>;
+			regulator-max-microvolt = <1393750>;
+			regulator-ramp-delay = <6250>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+
+		mt6380_vcore_reg: buck-vcore {
+			regulator-name = "vcore";
+			regulator-min-microvolt = <600000>;
+			regulator-max-microvolt = <1393750>;
+			regulator-ramp-delay = <6250>;
+		};
+
+		mt6380_vrf_reg: buck-vrf {
+			regulator-name = "vrf";
+			regulator-min-microvolt = <1200000>;
+			regulator-max-microvolt = <1575000>;
+			regulator-ramp-delay = <0>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+
+		mt6380_vm_reg: ldo-vm {
+			regulator-name = "vm";
+			regulator-min-microvolt = <1050000>;
+			regulator-max-microvolt = <1400000>;
+			regulator-ramp-delay = <0>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+
+		mt6380_va_reg: ldo-va {
+			regulator-name = "va";
+			regulator-min-microvolt = <2200000>;
+			regulator-max-microvolt = <3300000>;
+			regulator-ramp-delay = <0>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+
+		mt6380_vphy_reg: ldo-vphy {
+			regulator-name = "vphy";
+			regulator-min-microvolt = <1800000>;
+			regulator-max-microvolt = <1800000>;
+			regulator-ramp-delay = <0>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+
+		mt6380_vddr_reg: ldo-vddr {
+			regulator-name = "vddr";
+			regulator-min-microvolt = <1240000>;
+			regulator-max-microvolt = <1840000>;
+			regulator-ramp-delay = <0>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+
+		mt6380_vt_reg: ldo-vt {
+			regulator-name = "vt";
+			regulator-min-microvolt = <2200000>;
+			regulator-max-microvolt = <3300000>;
+			regulator-ramp-delay = <0>;
+			regulator-always-on;
+			regulator-boot-on;
+		};
+	};