dt-bindings: input: touchscreen: add minimum pressure touchscreen property

Add a common touchscreen optional property that will specify
the minimum pressure applied to the screen that is needed
such that the driver will report the touch event.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

@@ -7,6 +7,9 @@ Optional properties for Touchscreens:
 				  (in pixels)
  - touchscreen-max-pressure	: maximum reported pressure (arbitrary range
 				  dependent on the controller)
+ - touchscreen-min-pressure	: minimum pressure on the touchscreen to be
+				  achieved in order for the touchscreen
+				  driver to report a touch event.
  - touchscreen-fuzz-x		: horizontal noise value of the absolute input
 				  device (in pixels)
  - touchscreen-fuzz-y		: vertical noise value of the absolute input