I'm glad Linus didn't miss that the change was just a user of the DMA code and didn't involve any changes to DMA itself. I think that very important point was overlooked in many of the responses in the original thread.
Here are parts of a mail from Danilo Krummrich [1] in the thread that started all of this:
> As explained previously, this component is just a user of the DMA coherent allocator API (just like any other driver)
> Being a maintainer myself, I think it is outside the scope of a maintainer to restrict the usage of a public kernel API for a certain entity arbitrarily and / or by personal preference, which, as it appears to me, is the case here.
Emphasis is mine. This shows that the point was repeatedly raised. You can see for yourself what the response was. Besides, the only way to miss that point is to not look at the patch at all.