mfd: devicetree: bindings: Document PM8921/8058 PMICs

PM8921 and PM8058 are PMICs found paired with MSM8960 and MSM8660
devices respectively. They contain subdevices such as keypads,
RTC, regulators, clocks, etc.
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/qcom,pm8xxx.txt

+Qualcomm PM8xxx PMIC multi-function devices
+
+PROPERTIES
+
+- compatible:
+	Usage: required
+	Value type: <string>
+	Definition: must be one of:
+		    "qcom,pm8058"
+		    "qcom,pm8921"
+
+- #address-cells:
+	Usage: required
+	Value type: <u32>
+	Definition: must be 1
+
+- #size-cells:
+	Usage: required
+	Value type: <u32>
+	Definition: must be 0
+
+- interrupts:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: specifies the interrupt that indicates a subdevice
+		    has generated an interrupt (summary interrupt). The
+		    format of the specifier is defined by the binding document
+		    describing the node's interrupt parent.
+
+- #interrupt-cells:
+	Usage: required
+	Value type : <u32>
+	Definition: must be 2. Specifies the number of cells needed to encode
+		    an interrupt source. The 1st cell contains the interrupt
+		    number. The 2nd cell is the trigger type and level flags
+		    encoded as follows:
+
+			1 = low-to-high edge triggered
+			2 = high-to-low edge triggered
+			4 = active high level-sensitive
+			8 = active low level-sensitive
+
+- interrupt-controller:
+	Usage: required
+	Value type: <empty>
+	Definition: identifies this node as an interrupt controller
+
+EXAMPLE
+
+	pmicintc: pmic@0 {
+		compatible = "qcom,pm8921";
+		interrupts = <104 8>;
+		#interrupt-cells = <2>;
+		interrupt-controller;
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		pwrkey {
+			compatible = "qcom,pm8921-pwrkey";
+			interrupt-parent = <&pmicintc>;
+			interrupts = <50 1>, <51 1>;
+		};
+	};