Ah. Then you need to add a Rails model and then also add a model to Ember. I have done it several times and still find it very confusing.
Check out an other plugin that adds a route. Subscriptions is one, but you might also get GitHub - discourse/all-the-plugins · GitHub and then do a find for “route*”. The Rails part is in config and the Ember part is in assets/javascripts/discourse/routes.