A “camp site where only campervans are allowed” is tourism=caravan_site. That may sound weird, but it’s just a label - refer to the wiki to see what it really means. This includes things that look like “designated parking spaces for campers”, if overnight stay is explicitly allowed. If you want to avoid confusion, you could follow the advise here to add caravan=no and motorhome=yes. If I were traveling with a caravan, I wouldn’t trust I could use any caravan_site that did NOT have a caravan=yes tag (i.e. in Europe it feels like the default is no and people don’t add that tag often).
