dt-bindings: regulator: document stpmic1 pmic regulators

The STPMIC1 regulators supply power to the application processor as well as
to the external system peripherals such as DDR, Flash memories and system
devices.
Signed-off-by: pascal paillet <p.paillet@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/st,stpmic1-regulator.txt

+STMicroelectronics STPMIC1 Voltage regulators
+
+Regulator Nodes are optional depending on needs.
+
+Available Regulators in STPMIC1 device are:
+  - buck1 for Buck BUCK1
+  - buck2 for Buck BUCK2
+  - buck3 for Buck BUCK3
+  - buck4 for Buck BUCK4
+  - ldo1 for LDO LDO1
+  - ldo2 for LDO LDO2
+  - ldo3 for LDO LDO3
+  - ldo4 for LDO LDO4
+  - ldo5 for LDO LDO5
+  - ldo6 for LDO LDO6
+  - vref_ddr for LDO Vref DDR
+  - boost for Buck BOOST
+  - pwr_sw1 for VBUS_OTG switch
+  - pwr_sw2 for SW_OUT switch
+
+Switches are fixed voltage regulators with only enable/disable capability.
+
+Optional properties:
+- st,mask-reset: mask reset for this regulator: the regulator configuration
+  is maintained during pmic reset.
+- regulator-pull-down: enable high pull down
+  if not specified light pull down is used
+- regulator-over-current-protection:
+    if set, all regulators are switched off in case of over-current detection
+    on this regulator,
+    if not set, the driver only sends an over-current event.
+- interrupt-parent: phandle to the parent interrupt controller
+- interrupts: index of current limit detection interrupt
+- <regulator>-supply: phandle to the parent supply/regulator node
+	each regulator supply can be described except vref_ddr.
+
+Example:
+regulators {
+	compatible = "st,stpmic1-regulators";
+
+	ldo6-supply = <&v3v3>;
+
+	vdd_core: buck1 {
+		regulator-name = "vdd_core";
+		interrupts = <IT_CURLIM_BUCK1 0>;
+		interrupt-parent = <&pmic>;
+		st,mask-reset;
+		regulator-pull-down;
+		regulator-min-microvolt = <700000>;
+		regulator-max-microvolt = <1200000>;
+	};
+
+	v3v3: buck4 {
+		regulator-name = "v3v3";
+		interrupts = <IT_CURLIM_BUCK4 0>;
+		interrupt-parent = <&mypmic>;
+
+		regulator-min-microvolt = <3300000>;
+		regulator-max-microvolt = <3300000>;
+	};
+
+	v1v8: ldo6 {
+		regulator-name = "v1v8";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+		regulator-over-current-protection;
+	};
+};