I just transited through there on QR a few days ago. There are different arrival areas for transiting and true "arriving (entering DOH)" passengers. If you are transiting you go through x-ray and go right to transit gates. If arriving I assume you go through normal arrival procedures. You can probably just go to the transit area. You are bussed from the plane. I don't know how other airlines handle it but QR gives you onward boarding passes that match the colors of the arrival areas (yellow is transit, e.g.). There are people checking when you get off the plane to make sure you go to the right area. Other airlines might not do that but they have to get you to the correct arrival area. This all assumes that you only have carry-on luggage.