How do I get my BCM43228 card working in mainline kernel 3.4 or higher?

If you read the wiki, might I draw your attention to this bit:

By definition the mainline kernel builds are made from virgin unaltered mainline kernel sources and therefore do not, and should not, include any Ubuntu patches or drivers. There are also no binary drivers for these kernels.

Rather than the mainline builds, you will usually have better luck with the kernels for the next alpha/beta version (in this case, 12.10 Quantal Alpha 2), which should have binary drivers available:

1. Get the 12.10 bcmwl-kernel-source package from the below link and try installing it with dpkg:

   http://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu/pool/restricted/b/bcmwl/bcmwl-kernel-source_5.100.82.112%2bbdcom-0ubuntu2_amd64.deb
   

2. If that doesn't work on your mainline build, install the 12.10 3.5 kernel images/headers, and then try again:

   http://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu/pool/main/l/linux/linux-headers-3.5.0-4_3.5.0-4.4_all.deb
   http://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu/pool/main/l/linux/linux-headers-3.5.0-4-generic_3.5.0-4.4_amd64.deb
   http://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu/pool/main/l/linux/linux-image-3.5.0-4-generic_3.5.0-4.4_amd64.deb
   http://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu/pool/main/l/linux/linux-image-extra-3.5.0-4-generic_3.5.0-4.4_amd64.deb
   

Note: Since you look like someone who should be fairly handy with this :), may I recommend you consider replacing the awful binary-only Broadcom card with one of the excellent Intel 6205 or 6300 half-mini-PCIe cards, which have fully open-source driver support in the vanilla kernel?

Had the same problem with the kernel package I downloaded from xorg-edgers. I then downloaded the quantal version of bcmwl-kernel-source from here, installed it and my wireless card worked immediately.