And it probably needs hyphens. Door-to-door salesman. He goes from door to door.

And a doorman is not a door-to-door man. A doorman attends the door of a hotel or apartment block etc.

Your video clip is a joke. It's a visual pun. Wendy's definitions are correct. I can't hear the sound in this video clip. In this video clip, there are no "doormen." In this video clip, we see two "door-to-door salesmen." There are very few door-to-door salespeople in the U.S. any more, but in the past they were typically selling things like brushes, magazines, vacuum cleaners, or encyclopedias. I believe Avon and so others still sell cosmetics that way. You could speak of a "door-to-door vacuum cleaner salesman" or a "door-to-door encyclopedia salesman." The joke here is that they are selling DOORS. So, they are "door salesmen," they are "door-to-door salesmen," and they are "door-to-door door salesmen." However it's a fairly silly joke because nobody sells doors that way--and if they did, they wouldn't use a full-sized door, they'd bring a catalog and perhaps some miniature door samples. It sounds from your description as if they take the joke to another level--one of the salesmen is a door-to-door door salesman, and the other is selling SALESMEN. Specifically, he is selling a door-to-door door salesman. Hence--using brackets in the style of a computer language--he is "a door-to-door [door-to-door door salesman] salesman." Sounds like the kind of humor Lewis Carroll, author of "Alice's Adventures in Wonderland," might have enjoyed...

A door to door man travels around selling things door to door. In other words, he (and it is usually a he) bangs on one door and tries to sell his wares. Then he goes to the next house and the next door. It's a hard life, I think.