The word for a place where buses pick up and drop off passengers is conventionally spelled as two words—bus stop. Some similar phrases fuse into compounds (e.g., stoplight, snowman, headstone), but bus stop has never gone this route, perhaps because the two s‘s would be awkward. For now, busstop is considered a misspelling.
Examples
Then the grandma from our hotel kindly shows us how to get to the bus stop. [Washington Post]
Meanwhile the group will be selling local vegetable bags at the King’s Buildings bus stop this afternoon. [The Guardian]
She ran away one afternoon, but the headmistress intercepted her at the bus stop. [Globe and Mail]
… a snow-covered Lexus SUV, parked squarely in the middle of a bus stop. [Boston Globe]