Valve's Pierre-Loup Griffais announced on Twitter that they've hired Andrey Smirnov to help them get some SteamOS changes upstream into the main Linux Kernel.
Here's what he said:
Andrey is a kernel developer we're hired to help us upstream various SteamOS driver changes, as well as undertake other kernel projects. First stop: Xbox One S rumble support!
You can see the post they're talking about on the Linux Kernel Mailing List archive. It will have to go through the usual process of getting feedback and possibly going through revisions before being accepted for a future Linux Kernel release.
While there is also the xpadneo driver for the Xbox One S gamepad, having more work out of the box is obviously a good thing for everyone. This is probably also useful for Valve as well, since it's one less thing they will need to maintain themselves for SteamOS directly.