Ember dynamic route with nested route inside it

I am kind of new to ember .. and i am having a little problem

the problem is that i want to generate a route with an id and another

nested route inside it for example "doctors/visit/(the visit id)/order

here is my router file

this.route('doctor', function() {
    this.route('visit', {path:'/visit/:visit_id'});
});

my visit file

import Ember from 'ember';

export default Ember.Route.extend({
  model(params){
    return this.store.findRecord('visit',params.visit_id);
  }
});

how can i reference one level new route to make it like the one i wrote in the example ?