"Generally Ubuntu systems run with the stock Ubuntu kernels. However it is handy to be able to test with unmodified mainline kernels to help locate problems in the Ubuntu kernel patches, or to confirm that upstream has fixed the issue. To this end we now offer mainline kernel builds. These mainline kernels are made from unmodified kernel source but using the Ubuntu kernel configuration files. These are then packaged as Ubuntu .deb files for simple installation."
https://wiki.ubuntu.com/KernelMainlineBuilds
