Ubuntu team releases custom kernels for its distribution.
For example, my current is 4.4.0-53 while last stable is 4.8.15 and last longterm is 4.4.39 (both according to kernel.org). Searching didn't revealed clearly the way Ubuntu team patches upstream kernel to ship it.
What patches does it apply to upstream kernel, what does it backport from upstream kernel code?
How would one correlate version strings like 4.4.0-53 to vanilla kernel numbering scheme?