I’m not sure why you think manufactuers of SoCs - which aren’t used by Google directly - provide drivers to Google. They don’t, because there is no point in doing that. This is not how the Android eco-system works or the business of selling those SoCs for that matter. SoC manufactuers sell their SoCs to companies who want to build Android phones (or they build their own like Samsung). With those SoCs they provide a BSP (board support package) that includes all the bits needed to bring up a system running on that partricular SoC. Google has pretty much nothing to do with this, except that Google recommends a certain Linux kernel version (with a bunch of Android-specific patches) for a given Android version, which SoC makers often (but not always) use as the base for their customized kernels.

It is not like Google provides the operating system including all device specific drivers to the device manufacturers. They don’t care about that at all. They provide AOSP (which is open source, so anyone can get that) as well as their proprietary stuff like Google Play etc. That’s pretty much it.