I don't know how much you know about door frames so I'll try to cover everything.. the part of the door frame that carries most of the weight is called the plain casing. This is normally made out of 4x3in but it may be bigger depending on the size of the opening, walls or weight of the door. Some doors can weigh over 200kg in extreme cases.
You also might think of the area the house is in, many newer houses don't have rebates (rabbets?) in the plain casing. These frames have a separate piece of timber nailed on as the door stop.
Most will be mortise and tennoned and glued and screwed. Softwood is generally frowned upon and hardwoods seem to be preferred. Mahogany and the like.
The door frame is fixed to the masonry mostly by plugs and screws and a matching dowel will cover the screw head. An alternative and old method is to fix a piece of wood behind the frame and screw through that and when the door trims go up, it is concealed.