Using the drop-in tree
Once you have the appropriate module checked out for your kernel, you may notice that there are quite a few files missing. This is due to the fact that the only files tracked in the drop-in tree are files where we need to make SH-specific changes. This keeps maintenance down, and ultimately results in a much smaller download.
Linking the drop-in tree to the source tree
We ship a couple of scripts with the module to ease the task of "dropping in" the drop-in tree. These scripts exist as scripts/treelink.sh and scripts/treeunlink.sh. The name of the scripts should give enough explanation as to their purpose.
The script treelink.sh takes two arguments: a drop-in tree directory, and a kernel source directory to apply it to. If you're in the scripts/ directory, you could run a command similar to the following:
$ ./treelink.sh ../../<drop-in tree dirname> <kernel source tree name>
This will subsequently symlink all of the drop-in tree components over top of the stock kernel ones, resulting in a full kernel tree ready for development and building.
Updating the kernel source tree
Naturally, there will be ongoing updates to the drop-in tree that you'll want to add to your working tree. With arch, you can check if there are any updates to your drop-in tree, and get those updates, by running these commands inside the top-level directory of the tree:
$ tla missing $ tla missing --summary # surprisingly, more verbose $ tla update # get all updates
If there were changes that still correspond to the same kernel version, you can use the treeunlink.sh script to undo the SH-related additions to the kernel tree, then relink with the newer drop-in tree.