devicetree: power/mfd: max77693: Document new bindings for charger

Document new device tree bindings for Maxim 77693 charger driver.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

Documentation/devicetree/bindings/mfd/max77693.txt

···
 	 To get more informations, please refer to documentaion.
 	[*] refer Documentation/devicetree/bindings/pwm/pwm.txt
 
+- charger : Node configuring the charger driver.
+  If present, required properties:
+  - compatible : Must be "maxim,max77693-charger".
+
+  Optional properties (if not set, defaults will be used):
+  - maxim,constant-microvolt : Battery constant voltage in uV. The charger
+    will operate in fast charge constant current mode till battery voltage
+    reaches this level. Then the charger will switch to fast charge constant
+    voltage mode. Also vsys (system voltage) will be set to this value when
+    DC power is supplied but charger is not enabled.
+    Valid values: 3650000 - 4400000, step by 25000 (rounded down)
+    Default: 4200000
+
+  - maxim,min-system-microvolt : Minimal system voltage in uV.
+    Valid values: 3000000 - 3700000, step by 100000 (rounded down)
+    Default: 3600000
+
+  - maxim,thermal-regulation-celsius : Temperature in Celsius for entering
+    high temperature charging mode. If die temperature exceeds this value
+    the charging current will be reduced by 105 mA/Celsius.
+    Valid values: 70, 85, 100, 115
+    Default: 100
+
+  - maxim,battery-overcurrent-microamp : Overcurrent protection threshold
+    in uA (current from battery to system).
+    Valid values: 2000000 - 3500000, step by 250000 (rounded down)
+    Default: 3500000
+
+  - maxim,charge-input-threshold-microvolt : Threshold voltage in uV for
+    triggering input voltage regulation loop. If input voltage decreases
+    below this value, the input current will be reduced to reach the
+    threshold voltage.
+    Valid values: 4300000, 4700000, 4800000, 4900000
+    Default: 4300000
+
 Example:
 	max77693@66 {
 		compatible = "maxim,max77693";
···
 			haptic-supply = <&haptic_supply>;
 			pwms = <&pwm 0 40000 0>;
 			pwm-names = "haptic";
+		};
+
+		charger {
+			compatible = "maxim,max77693-charger";
+
+			maxim,constant-microvolt = <4200000>;
+			maxim,min-system-microvolt = <3600000>;
+			maxim,thermal-regulation-celsius = <75>;
+			maxim,battery-overcurrent-microamp = <3000000>;
+			maxim,charge-input-threshold-microvolt = <4300000>;
 		};
 	};