Couple of nits.
This return code is repeated several times. Maybe a section on common return codes isn't bad?
I think s/is drought/is being drawn/ here. drought is weather where there's little water for a long time...
I don't think micro-volts is hyphenated, but rather is just one word.
and it returns ENOENT if ofw property doesn't exist . The one can use this for detection optional regulator properties ( to distinguish property presence from other errors).
it returns EBUSY if any other consumer have it actually enabled (thus if regulator is shared and other driver have it enabled).