Raspberry PI talking to Arduino UNO

Just connected my brand new Raspberry PI and Arduino via serial comm. Arduino is flashing LED’s a number of times that’s received from Raspberry. Just fun. Next step is to control the Raspberry wireless (using ICIDU Nano USB 150N adapter) and let him drive Arduino to controle a steering servo on a LEGO car. The final solution should be an wireless, battery powered car, controlled by a steering app on an Android device.