[PATCH v3 2/4] mfd: max77620: add documentation for backup battery charging

[Mark Zhang]

Adding documentation for 3 new backup battery charging dts
properties:
- maxim,charging-current-microamp
- maxim,charging-voltage-microvolt
- maxim,output-resister-ohms

Signed-off-by: Mark Zhang <markz@xxxxxxxxxx>
---
 .../devicetree/bindings/mfd/max77620.txt      | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Documentation/devicetree/bindings/mfd/max77620.txt b/Documentation/devicetree/bindings/mfd/max77620.txt
index 9c16d51cc15b..88825eaf2567 100644
--- a/Documentation/devicetree/bindings/mfd/max77620.txt
+++ b/Documentation/devicetree/bindings/mfd/max77620.txt
@@ -122,6 +122,26 @@ For DT binding details of different sub modules like GPIO, pincontrol,
 regulator, power, please refer respective device-tree binding document
 under their respective sub-system directories.
 
+Backup Battery:
+==============
+This sub-node configure charging backup battery of the device. Device has
+support of charging the backup battery. The subnode name is "backup-battery".
+The property for backup-battery child nodes as:
+Presence of this child node will enable the backup battery charging.
+
+Optional properties:
+	-maxim,charging-current-microamp: Charging current setting.
+			The device supports 50/100/200/400/600/800uA.
+			If this property is unavailable then it will
+			charge with 50uA.
+	-maxim,charging-voltage-microvolt: Charging Voltage Limit Setting.
+			Device supports 2500000/3000000/3300000/350000uV.
+			Default will be set to 2500mV. The voltage will be roundoff
+			to nearest lower side if other than above is configured.
+	-maxim,output-resister-ohms: Output resistor on Ohm.
+			Device supports 100/1000/3000/6000 Ohms.
+			Default will be set to 1000 Ohm.
+
 Example:
 --------
 #include <dt-bindings/mfd/max77620.h>
-- 
2.19.2