iPhone 12 ProMax re-purpose and use only as a camera

Hi All

Anyone know anything about the following scenario: We keep our current iPhone 12 ProMax, buy the current iPhone version (14) and then want to re-purpose the 12 as a stand alone camera (no phone functions/phone number etc) while the new iPhone becomes our new, fully functional, totally normal, 'in all iPhone ways' device? If so, where can I find the info, process etc etc blah blah blah...Thanks for reading our post... Best for the 'New Year' DB