http://www.synaptics.com/sites/default/files/511-000136-01-Rev-E-RMI4-Interfacing-Guide.pdf
Optional Touch Properties:
-Description in Documentation/devicetree/bindings/input/touch
+Description in Documentation/devicetree/bindings/input/touchscreen
- touchscreen-inverted-x
- touchscreen-inverted-y
- touchscreen-swapped-x-y