It is not "restricted", they are called "regulated" and no, you have to do nothing at all. You do not have to register them or tell the state you brought them with you whatsoever. Registration in MD is voluntary except for full auto.
There are items called "assault pistols" which are prohibitted like a Tec 9 or an Uzi pistol, but most of the pistols on the list haven't even been made of fifteen years and it is not that long of a list anyway. If you have one of these semi auto pistols, then don't bring it.
# An assault pistol is defined as any of the following specified firearms or their copies regardless of which company produced and manufactured the firearm:
AA Arms AP-9 semi-automatics
# Bushmaster semi-automatic pistol;
# Claridge HI-TEC, semi-automatic pistol;
# D Max Industries semi-automatic pistol;
# Encom MK-IV, MP-9, MP-45 semi-automatic pistols;
# Heckler and Koch semi-automatic pistol SP-89;
# Holmes MP-83 semi-automatic pistol;
# Ingram MAC 10/11 semi-automatic pistol and any variation including the Partisan Avenger and the SWD Cobray;
# Intratec TEC-9/DC-9 in any centerfire variation;
# P.A.W.S. type semi-automatic pistol;
# Skorpion semi-automatic pistol;
# Spectre double action semi-automatic pistol (Sile, F.I.E., Mitchell);
# UZI semi-automatic pistol;
# Weaver Arms semi-automatic Nighthawk pistol; and
# Wilkinson semi-automatic "Linda" pistol.
MD Firearms Safety Training