Unfortunately, we don’t have such a policy, very similarly to how we lack even more basic policies (people are complaining about that these days in this thread). However, in my experience, if 1 person is able to verify the change is working with the hardware, or even if none, and the changes look good and software at least compiles and is able to not crash for a --help argument, it should be good to go.
For the 1st PR you linked, getting a 
from that person who requested the feature would greatly benefit, after most of the review is done.