https://tinker-board.asus.com/forum/index.php?/topic/15183-only-ttymxc0-and-ttymxc1-are-checked-in-the-list-is-this-normal/
Only ttymxc0 and ttymxc1 are checked in the list, is this normal? - Software - Tinker Board Forum
My tinker edge t board has two UARTs, ttymxc0 and ttymcx1. If you dont see ttymxc2 in the get start documentation, it says to do sudo apt-get dist-upgrade....