door frame
wooden or metallic framework that is slightly bigger than the door it supports and that consists of two parallel upright members (side jambs) on top of which rests a horizontal member (head jamb or lintel). It may include a sill at the bottom
en-US/ˈdɔɹ ˈfɹeɪm/
en-GB/ˈdɔː ˈfɹeɪm/