Document all possibilities to get a serial console
AFAIK (vaguely from a past discussion) there's (at least) 3 ways to have a console:
- software: via Linux as a USB gadget device, i.e. /dev/ttyACM0
- hardware: via USB-C pins? how exactly? breakout board?
- hardware: via dedicated "accessible" points to solder a cable / connector to. (which one? where are they?)
the "hardware" ones are especially important for development and "power users".
@eric.kuzmenko and @angus.ainslie will know much more here though. Is that already informally documented in some issue or elsewhere? If not, can we summarize here?