入口 and 玄関: a facility entrance and a building’s entry area
Compare entrances to a parking area and park with fixtures in a building’s entry area, without treating every entrance as a foyer.
A way into a facility or space
入口, read いりぐち, means entrance. 駐車場の入口で係員に聞きました。 says that someone asked an attendant at the parking-area entrance.
公園の入口に地図があります。 locates a map at the park entrance. 入口 is not limited to a building.
The entry area of a building
玄関, read げんかん, names the entry area of a house or building. 玄関に傘立てがあります。 says that an umbrella stand is in the entry area.
玄関の照明をつけました。 says that someone turned on the entrance lighting. 照明 is what was switched on, rather than treating the whole entrance as an operated object.
Overlap and different facility references
入口 and 玄関 can overlap for a building entrance. But 駐車場の入口 identifies access to the parking area, so do not change it into a house’s entry space.
玄関の外に立っています。 says that someone is standing outside the entry area. 玄関 is the location reference, and completed entry is not stated.
Does 駐車場の入口で establish that someone was inside a building’s entry area?
Show the answer and why
No. It identifies the parking-area entrance without stating a position inside a building’s entry area.