app.js

App.ProjectsController = Ember.ArrayController.extend({
	cancel: function() {
    // Do something
  }
});

App.ProjectsNewController = Ember.ArrayController.extend({
	create: function() {
		// Do something
	}
});

projects_new.hbs

<form {{ action 'create' on='submit'}} class="form-horizontal"> <!-- this triggers create on the ProjectsNewController -->
<!-- Fields here -->
<button type="submit" class="btn btn-success">Add task</button> 
<a {{action 'cancel'}} class="btn">Cancel</a> <!-- Can this trigger the cancel on ProjectsController? -->
</form>