On Tue, Sep 18, 2018 at 08:27:11AM -0700, Christoph Hellwig wrote:

> I did that for the SCSI tree a long time ago, and it did not work out
> at all as the few core changes are usually required by driver changes.

> Note that I've not really seen the split recently in the block tree
> either, probably for the same reason.

Most of my topic branches end up being per-driver ones, with embedded
stuff that often winds up being useful for cross tree merges that
weren't anticipated.  The core changes that affect or are used by
drivers either get the relevant driver changes stacked onto the same
branch or merged into the driver branches depending on taste.