What are these and how do I get rid of them? Little white creepy crawlies?

Hello 🙂 we have a problem!
we are dealing with small white creepy crawlies…
They're mostly found on clothing (eg, on coats in the entrance), but also on backpacks left there, and they seem to be spreading to the furniture as well. I'm even finding them on freshly washed laundry, even if it's been sitting in the laundry basket for a day before I've had time to iron it…
I think it all started when I bought a new coat for my son. A few days after the purchase, I noticed the little creatures on it for the first time. Lots of them! (down jacket)

Well, I washed the new coat and all the others that were nearby, but the problem persists and is spreading. The little creatures are tiny, barely visible, but they're definitely moving (quite slowly). I suspect they're some kind of mite?
How do I get rid of them?

I'm afraid they're all over the house now :-/