I used to be part of a psychiatric home-care team 10-15 years ago. I provided intermittent visits to the patient's home, operating under a form 485 signed by a psychiatrist.
IIRC, Medicare required two years of psychiatric experience in order to qualify as a billable visit. There was talk of creating the standard of mandatory psych certification, but that didn't happen.
I don't know the current regs, but I would guess that "psych visits" by a non-psych RN would not be a billable visit
It's good that you are asking this question. Of course, I'd also ask the employer and see what they say.