Support for Tinkerboard2

[SteMMo33]

Hello Arne,
what about to add the support for Tinkerboard2 ?

Thanks,
regards

[arne48]

Theoretically it would be nice to also add ASUS' new Tinkerboard using the RK3399 to this library.
Unfortunately it's currently complicated to get a Tinkerboard 2 in Japan and also after a brief search I couldn't find a datasheet including the description for all the registers needed to control the functions of the GPIO pins and controllers like SPI.
If you have access to such I would be welcoming any contribution to this repository regarding the support of the Tinkerboard 2.