Hi,
As far as I know the touchscreen acts as an input device.
You can find a very simple example of an input device driver in the linxu documentation:
Documentation/input/input-programming.txt
And the existing drivers may be helpful to understand the Linux API for the input device drivers.
But before doing that you need to understand how the touch controller sends the touch reports and I have not found the datasheet or the document that contains such information. If you have somethig please feel free to share it.
Best Regards,
Alejandro