It would be helpful if you ran "lscpi -v" and "lspci -n". For the latter, you will get the manid of the device, which helps us look up the kernel module used. Your description would be one of these (from /usr/share/pci.ids)
1361 BCM4312 802.11a/b/g WLAN Controller
1371 Broadcom Corporation BCM4312 802.11a/b/g (rev 02)
It looks like this device uses the b43 or b43legacy, you need to download a driver and use b43-fwcutter to cut out and save the firmware in /lib/firmware/.
I used to have a laptop with a broadcom wireless device, and installed Fedora on it. I used an openSuSE script to download and install the firmware using b43-fwcutter. It uses the firmware on the wrt site, and works for b43 and b43legacy.