No you can't do that... if you bringSubviewToFront A then its all subviews are showing above on B.
In that case you have to hidden subview which you dont want to see.
You can use below methods to for showing A on top.
[A.superview bringSubviewToFront:A];
Or you can put B below A with this method.
[B.superview sendSubviewToBack:B];