YourApp.someArrayController = SC.ArrayController.create({
  someAction: function (x,y) {
    var sel = this.getPath('selection');
  }
});

// parent view code
  something: SC.ListView.extend({
    contentBinding: 'YourApp.someArrayController.content',
    selectionBinding: SC.Binding.from('YourApp.someArrayController.selection').single(),
  }),

  someButton: SC.ButtonView.extend({
    action:'someAction',
    target: YourApp.someArrayController
  })
// end parent view code