https://stackoverflow.com/questions/44725752/calling-a-function-on-a-component-from-the-controller

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  didInsertElement(){
    this.get('registerComponent')(this);
  },
  willDestroyElement(){
    this.get('deregisterComponent')();
    this._super(...argument);    
  },
  sayHi(){
   alert(' Hi from component');
  }

});

controllers.application.js

import Ember from 'ember';
export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  componentRef:null,
  actions:{
    registerComponent(componentRef){
      this.set('componentRef',componentRef);
    },
    deregisterComponent(){
      this.set('componentRef',null);
    },
    callComponentMethod(){
        this.get('componentRef').sayHi();
      }
  }
});

templates.application.hbs

<h1 {{action 'callComponentMethod'}}>Welcome to {{appName}}</h1>
<br>
{{my-component registerComponent=(action 'registerComponent') deregisterComponent=(action 'deregisterComponent')}}
<br>
{{outlet}}
<br>
<br>

templates.components.my-component.hbs

<input type="text" id="name" />
{{yield}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}