LOL your experience in Windows driver land is in no way transferrable to Linux driver land.
My experience at Intel with drivers is directly transferable. Intel sells the whole product. That's why an OEM would choose Intel IP. It's a core part of the sales strategy at Intel, not Just PC, Servers too (even Linux servers). Especially to the smaller OEMs who don't have huge engineering teams. Name a server technology or Server component that didn't get mainlined or inbox'd of Intel's? Again, core to the sales strategy.
You mean for PCs running Windows.
Yes.
Which is not what we’re talking about.
Yes we are, "At the very least, the big laptop manufacturers". Lenovo, Asus, and MSI are PC OEMs that make Windows PCs. Laptops, Desktop, Workstations, and now Handheld PCs. Right now PC is dominated by Windows. If the SteamOS version of the Lenovo handhelds are a clear winner, other Windows PC OEMs will follow. They, the big laptop manufacturers, will bring their expectations with them. Just as AMD mainlined into Linux the drivers they did for their components in the Steam Deck, Intel will too. And that brings us back to, "the big laptop manufacturers making Linux handhelds means just from a cost cutting and resource perspective, there’s a good chance laptop and desktop hardware support improves even further just because they reuse parts across devices." If, the big laptop manufacturers, want the SteamOS name and branding, they will have to mainline and that means selecting IP that has or will have mainline drivers. Valve will not want to go the Google route and maintain a separate Linux Kernel.
Windows PC manufacturers, not 1 off ARM vendors.