Like the cmdline file we look for a devicetree file in
$KERNEL_INSTALL_CONF_ROOT, /etc/kernel and /usr/lib/kernel. If it is
present we look for the specified device tree that comes with the kernel
we're adding and install it into $ENTRY_DIR_ABS and add a devicetree
stanza to the loader entry.
Unfortunately it seems there is no common consensus on where to install
device tree blobs, so we have to look in a few different places for it.
projects / thirdparty / systemd.git / commit
