ISL3893
ISL 3893
This chipset can be found in a lot of routers. For a list of hardware see the isl3893.sf.net hardware page. I myself own a Fujitsu siemens AP600.
To create new firmware you need an ISL3893 Toolchain and the ISL3893 Source. You can get an ISL3893 quick start if you feel a bit scary diving into the deeps.
After creating the firmware you need to Flash the ISL3893.