Using gpio in MPC8309

Hello,

I just got a TWR-MPC8309 from Freescale running Embedded Linux OS. The kernel
version is Linux 2.6.11+pq3 patches and the kernel preconfig file is
linux_2.6.11_mpc8548_cds_def.config.

I'm new to processors running Linux and I'm having a hard time trying to
understand how can I program the GPIO and use them. Is there a tutorial or any
documentation you could provide me to get started on accessing the processor
pins please?

I'm using CodeWarrior Development Studio for Power Architecture version 10.0.2
and I haven't found a library that includes the functions to access the pins
functionality. Is there any documentation you could suggest me to do that please?