iPhone, ios8:如何显示比原始视图控制器小的视图控制器?

I have two view controllers, I want to present view controller(VC) of the first VC. Second VC have smaller size. I want to show second view controller over the first one. Like a popover. You can imagine it, if we add another view controller that slides from bottom to top but stops at navigation bar.I have two view controllers, I want to present