So far we do not have a ready to use example within the Raspberry Pi Build Environment that illustrates the integration with the underlying device. This is something that is still on our 'ToDo' List...
Nevertheless, there are two articles within our knowledge base that explains all necessary steps to make a proper device integration:
Integrating with the device
Device Class and Device Driver
In order to access the digital or analog I/O pins on a Raspberry Pi board, you can use popular GPIO interface library like WiringPi.
I hope this helps...