Earlier quoted context omitted.
That's not true, really. Many vendors keep their own in-house patches to the mainline tree, that never make it upstream for various reasons(See Android's kernel for instance). There is nothing stopping a vendor or anyone else, from publishing their own linux tree that is a fork of mainline with this AMD patch applied. Linus maintains the 'mainline' tree, just because of the history and because most kernel hackers bel…
Right. And this is an indicator that the Good King and his generals have done an exemplary job keeping it solid: Everyone uses their product.
Which are running a severely modified kernel because the process of going through mainline to get it mobile ready would be far too painful.