dt-bindings: touchscreen: add touch-overlay property

dt-bindings: touchscreen: add touch-overlay property

The touch-overlay encompasses a number of touch areas that define a
clipped touchscreen area and/or buttons with a specific functionality.

A clipped touchscreen area avoids getting events from regions that are
physically hidden by overlay frames.

For touchscreens with printed overlay buttons, sub-nodes with a suitable
key code can be defined to report key events instead of the original
touch events.

Reviewed-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
Link: https://lore.kernel.org/r/20241016-feature-ts_virtobj_patch-v11-1-b292a1bbb0a1@wolfvision.net
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>