Add common DT binding documentation for touchscreen devices and
implement input_parse_touchscreen_of_params, which parses the common
properties and configures the input device accordingly.

The method currently does not interpret the axis inversion properties,
since there is no matching flag in the generic linux input device.

Signed-off-by: Sebastian Reichel <sre@kernel.org>
---
 .../bindings/input/touchscreen/touchscreen.txt     | 27 +++++++++++++++++
 drivers/input/input.c                              | 34 ++++++++++++++++++++++
 include/linux/input.h                              |  8 +++++
 3 files changed, 69 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

diff --git a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
new file mode 100644
index 0000000..d8e0616
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

@@ -0,0 +1,27 @@
+General Touchscreen Properties:
+
+Optional properties for Touchscreens:
+ - touchscreen-size-x		: horizontal resolution of touchscreen
+				  (in pixels)
+ - touchscreen-size-y		: vertical resolution of touchscreen
+				  (in pixels)
+ - touchscreen-max-pressure	: maximum reported pressure (arbitrary range
+				  dependent on the controller)
+ - touchscreen-fuzz-x		: horizontal noise value of the absolute input
+				  device (in pixels)
+ - touchscreen-fuzz-y		: vertical noise value of the absolute input
+				  device (in pixels)
+ - touchscreen-fuzz-pressure	: pressure noise value of the absolute input
+				  device (arbitrary range dependent on the
+				  controller)
+ - touchscreen-inverted-x	: X axis is inverted (boolean)
+ - touchscreen-inverted-y	: Y axis is inverted (boolean)