Two ways. One, connect to laptop via usb, then get a crossover ethernet cable, connect from pc to ps3, then bridge the connection. Two, tether wirelessly (wifi tether) from the phone to ps3.
Keep in mind, this will work for your ps3 to access the internet. But if you think you will be able to play online games, you wont. The lag is HORRIBLE, not to mention a ping time that's usually between 100-300ms, when a normal internet connection is around 10ms. So you will have a very hard time playing any kind of action game at all.