The Raspberry Pi Foundation does not do a good upstream support. It is not very bad, but also not good. They should start adding support for their new chips in the upstream projects before they get into the market, like Intel does it for example. They could add support for some new IP cores, without reveling when and how it will be used later. When the product comes out the only add small patches linking the code together like device tree files.

It would also be good if they would release all the closed source firmware files needed for their devices under a redistributable license in the linux-firmware repository. For some time it was not allowed to redistribute the binary wifi firmware needed for the Raspberry Pi devices. This is needed for Linux distributions to package the binaries.

I hope they do this only because of lack of resources and not intentionally to lock people into their Linux distribution.

Virtually nobody uses mainline Linux on Raspberry Pis, so not sure why would it be so surprising.

If I went and checked commits, I’m sure there are a lot of business critical IOT/controller type processes that now rely on Raspberry and therefore engineers backing support out the gate