According to

> https://technet.microsoft.com/en-us/library/eb9b35a3-64e9-4c...

the central component that Microsoft requires is a code signing certificate (i.e. money and perhaps a little boring bureaucracy, which still can be done in a very systematic way). What Microsoft tests internally at the drivers is whether they have potential dangerous security bugs (e.g. buffer overflows). You can architect the drivers as you want to (though Microsoft provides guidelines and reference source code to make it easier to write drivers "the officially desired way").

Getting the drivers into the Linux kernel means - as one can see - going deeply into kernel politics. If Microsoft required something similarly, the hardware vendors would tap their forehead at Microsoft.