ARM: dts: qcom: Add binding for the qcom coincell charger

This binding is used to configure the driver for the coincell charger
found in Qualcomm PMICs.
Signed-off-by: NTim Bird <tim.bird@sonymobile.com>
Reviewed-by: NAndy Gross <agross@codeaurora.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/power/qcom,coincell-charger.txt

+Qualcomm Coincell Charger:
+
+The hardware block controls charging for a coincell or capacitor that is
+used to provide power backup for certain features of the power management
+IC (PMIC)
+
+- compatible:
+	Usage: required
+	Value type: <string>
+	Definition: must be: "qcom,pm8941-coincell"
+
+- reg:
+	Usage: required
+	Value type: <u32>
+	Definition: base address of the coincell charger registers
+
+- qcom,rset-ohms:
+	Usage: required
+	Value type: <u32>
+	Definition: resistance (in ohms) for current-limiting resistor
+		must be one of: 800, 1200, 1700, 2100
+
+- qcom,vset-millivolts:
+	Usage: required
+	Value type: <u32>
+	Definition: voltage (in millivolts) to apply for charging
+		must be one of: 2500, 3000, 3100, 3200
+
+- qcom,charger-disable:
+	Usage: optional
+	Value type: <boolean>
+	Definition: definining this property disables charging
+
+This charger is a sub-node of one of the 8941 PMIC blocks, and is specified
+as a child node in DTS of that node.  See ../mfd/qcom,spmi-pmic.txt and
+../mfd/qcom-pm8xxx.txt
+
+Example:
+
+	pm8941@0 {
+		coincell@2800 {
+			compatible = "qcom,pm8941-coincell";
+			reg = <0x2800>;
+
+			qcom,rset-ohms = <2100>;
+			qcom,vset-millivolts = <3000>;
+		};
+	};