Documentation: devicetree: Add Richtek RT9455 bindings

Signed-off-by: Anda-Maria Nicolae <anda-maria.nicolae@intel.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
[added default values to optional properties]
Signed-off-by: Sebastian Reichel <sre@kernel.org>

Documentation/devicetree/bindings/power/rt9455_charger.txt

@@ -0,0 +1,48 @@
+Binding for Richtek rt9455 battery charger
+
+Required properties:
+- compatible:				it should contain one of the following:
+					"richtek,rt9455".
+- reg:					integer, i2c address of the device.
+- interrupt-parent:			the phandle for the interrupt controller that
+					services interrupts for this device.
+- interrupts:				interrupt mapping for GPIO IRQ, it should be
+					configured with IRQ_TYPE_LEVEL_LOW flag.
+- richtek,output-charge-current:	integer, output current from the charger to the
+					battery, in uA.
+- richtek,end-of-charge-percentage:	integer, percent of the output charge current.
+					When the current in constant-voltage phase drops
+					below output_charge_current x end-of-charge-percentage,
+					charge is terminated.
+- richtek,battery-regulation-voltage:	integer, maximum battery voltage in uV.
+- richtek,boost-output-voltage:		integer, maximum voltage provided to consumer
+					devices, when the charger is in boost mode, in uV.
+
+Optional properties:
+- richtek,min-input-voltage-regulation: integer, input voltage level in uV, used to
+					decrease voltage level when the over current
+					of the input power source occurs.
+					This prevents input voltage drop due to insufficient
+					current provided by the power source.
+					Default: 4500000 uV (4.5V)
+- richtek,avg-input-current-regulation: integer, input current value in uA drained by the
+					charger from the power source.
+					Default: 500000 uA (500mA)
+
+Example:
+
+rt9455@22 {
+	compatible = "richtek,rt9455";
+	reg = <0x22>;
+
+	interrupt-parent = <&gpio1>;
+	interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
+
+	richtek,output-charge-current	    = <500000>;
+	richtek,end-of-charge-percentage    = <10>;
+	richtek,battery-regulation-voltage  = <4200000>;
+	richtek,boost-output-voltage	    = <5050000>;
+
+	richtek,min-input-voltage-regulation = <4500000>;
+	richtek,avg-input-current-regulation = <500000>;
+};