Work on the real-time patches for Linux started early in 2004 and has changed many parts of the kernel since them in a way to a better and more reliable behavior.
The 72 locking patches now merged for Linux 5.15 make up a large part of the remaining work, but as can be seen from linux-rt-devel's patches there still is more RT work to be upstreamed.
For those not relying and therefore building a real-time kernel, these patch series should have no impact on their Linux kernel.
Linutronix did a major part of this work over the last years as being the main contributor to the Linux Foundations Real-Time Linux project (https://wiki.linuxfoundation.org/realtime/start )