What changes often in Linux OS?

[pairofstrings]

TL;DR Summary

Linux has User-Space and Kernel-Space.

Can anyone tell me what the area is in Linux that doesn't change often?
We have System programming, Kernel Programming, Device Driver Programming which one of these are less frequently touched? By "change", I mean, how often -in System Programming or Kernel Programming or Device Driver Programming- the Linux creators modify the definition of function calls like "cdev_add()" or "fork()" or "spinlocks()" or "printk()"?
Thanks.

 

[nsaspook]

Look at https://www.kernel.org/ for the complete history of changes.

One of the largest changes (well worth the effort) was for device-tree in kernel drivers. I had to rewrite a few drivers to be compatible with that.
https://elinux.org/Device_Tree_Reference#Introduction
https://www.kernel.org/doc/html/latest/devicetree/usage-model.html

The base Kernel API is very stable for traditional kernel functions with most internal code changes being transparent to either space code functionality.
https://www.kernel.org/
https://www.kernel.org/doc/htmldocs/kernel-api/