Lovely. "Here's something that's simple and useful for users. Let's break it". What part of "we do not break userspace" do you not understand? Because that would be a user visible change.Huh? Commit bb29785e0d6d, which added support for assigning spi bus numbers via devicetree aliases, has been in the upstream Linux kernel since v3.9 which was released over three years ago.
The other saying is "if it is not upstream, it doesn't exist." That
said, I don't think we should remove it. Maybe some time later, but
first we need a suitable alternative.