The feature table here
https://github.com/AsahiLinux/docs/wiki/Feature-Support also tells you where along the path something is in terms of being stable and making it into the kernel. If it just has a release number like "5.19" then that means it was successfully upstreamed as part of that kernel version. Generally, the Asahi team tries to upstream as they go, but if they are uncertain about the overall architecture of a driver they'll hold off to prevent ossifying certain design decisions too early. An example of this is the GPU driver.