Okay, I managed to find a combination of CDBS debian/rules
binary-install target over-rides and debian/<package>.install
settings to avoid needing to move the files to the src/ directory, so
scratch #1.

#2 is however needed and is a trivial change - patch attached.

To support building the package using DKMS there are two changes I'd
like to see applied to the SVN tree and source packages.

1. Move all source files into a sub-directory src/
2. Alter the out-of-tree build detection variable

For (1) this is necessary to greatly simplify the preparation of
debianised packages by specifying final location of installed files
using the debian/<package>.install instructions. With this change the
file can simply contain:

src/*				usr/src/r5u870-0.11.1
debian/dkms.conf	usr/src/r5u870-0.11.1

Without it, the "src/*" line fails and it has to be replaced with a
complicated series of statements that avoid the debian/ directory and
its contents being included.

I've moved the entire package-root contents into src/ (including
README, COPYING, etc.) so that the package-root is empty of files and
has two directories:

debian/
src/

For (2), I found that the DKMS build would fail because the
KERNELRELEASE variable was being detected. I changed the variable to
PATCHLEVEL and the DKMS builds then work correctly.