To find the coordinate of subview in the view controller view coordinate system.

CoordinatesOfSubView.m

// Create nested subviews. self.view > subview1 > subview2

UIView *subview1 = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 20, 20, 300, 300);
[self.view addSubview:subview1];
UIView *subview2 = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 30, 30, 200, 200);
[superview addSubview:subview2];

// To find the coordinate of subview in the view controller view coordinate system.
CGPoint point = [subview1 convertPoint:subview2.frame.origin toView:self.view];