welcome 
typically wlan is placed within the br-lan bridge ( "brctl")... ip on wlan0 is more of a client ( STA ) or isolated network setup where it's bridged to an alternate bridge containing an alternate non-lan interface ( vlan or other ) ... then routed...
search the wiki/forum for "isolated wlan network" or maybe "guest network"/"wireless vlan" for more info...
that said... the Rpi might be slightly different from a typical router ( if for instance the internal wifi is mostly used for / capable of sta? )... I don't know about the Pi specifically....
have you read any wiki docs regarding it's setup?