How can I repair a rotted door frame?

To repair a rotted door frame, you can start by removing the rotted wood using a chisel and sanding the area smooth. Then, apply wood filler to the damaged area and let it dry. Once dry, sand the filler until smooth and paint or stain the frame to match the rest of the door. You can also consider reinforcing the frame with a metal or composite material for added strength and durability.