How free UART pin 8 and 10 from other processes

Hi,

I did a fresh install of Ubuntu 16.04 and installed the UPboard kernel like mentioned on
https://up-community.org/wiki/Ubuntu
Now I want to use the UART pin 8 and 10 ( GPIO 14+15 ) to communicate with some other serial instruments.

Can anybody tell me how to free this pins by other processes like Getty.
These processes are using the pins I want to use for myself like I did on the Pi3.

Thanks!