The flurry of contributions ensures that the Linux Kernel is released ever so frequently with updates that are normally way beyond developers’ expectations and indeed futuristic. If you are new to Linux Kernel or are even working on the same you should definitely know what are the major categories into which the Kernel is released normally?
As the name suggests mainline kernel tree is the place where all the new features are introduced and where all the new development generally happens. Normally a mainline Kernel is released every 2 to 3 months and is maintained by Linus Torvolds
Prepatch kernel otherwise known as ‘RC’ kernels is generally pre-releases of mainline kernel which is primarily targeted for developers working at the Kernel level or other keen Kernel enthusiasts. Basically prepatch Kernel contains non tested code that will later go into the mainline kernel, it contains new features and it must be compiled from the actual source. Prepatch kernel is maintained and released by Linus Torvolds
Normally mainline Kernel is considered to be a stable release. However any bug fixes for a stable kernel is backported from the mainline tree and applied by a designated stable kernel maintainer. Normally two things could happen when a kernel moves from mainline to a stable version; one is that bug fixes if any will happen and versions will be released and it could reach an EOL (End of life) state which means Kernel maintainers will no longer provide bug fixes for the version, as it is considered stable and two the kernel could be pushed to Longterm Support Kernel
Kernel maintainers will provide bug fixes for this kernel version for a longer period of time. This will help in backporting bugfixes for older kernel tree. One of most stable and popular Kernel version 2.6.32 which was released in 2003 has a projected EOL till 2016
Hope you had some insight into how Linux Kernels are released and what they mean for a developer.