add 3rd party/custom patches

3rd patchs (in alphabetical order):
- bbr3
- ntsync5
- openwrt
- pf-kernel
- xanmod
- zen

no configuration changes for now

debian/bin/genpatch-pfkernel

@@ -0,0 +1,61 @@
+#!/bin/sh
+set -ef
+
+export GIT_OPTIONAL_LOCKS=0
+
+w=$(git rev-parse --path-format=absolute --show-toplevel) ; : "${w:?}" ; cd "$w"
+
+dst='debian/patches/pf'
+src='../linux-extras'
+branches='amd-pstate amd-rapl cpuidle crypto fixes ksm zstd'
+
+[ -d "${dst}" ]
+
+kver=
+if [ -n "$1" ] ; then
+	kver="$1"
+else
+	kver=$(dpkg-parsechangelog --show-field=Version | sed -E 's/^[0-9]+://;s/-[^-]*$//' | cut -d. -f1-2)
+fi
+from="upstream/linux-${kver}.y"
+
+t=$(mktemp -d) ; : "${t:?}"
+
+cp -ar "${src}" "$t/"
+cd "$t/${src##*/}"
+
+git config advice.skippedCherryPicks false
+
+for b in ${branches} ; do
+	ref="pf/$b-${kver}"
+	r="tmp-rebase-$b"
+
+	git switch --detach "${ref}"
+	git switch -C "$r"
+
+	if git rebase "${from}" ; then
+		[ -d "$w/${dst}/$b/" ] || mkdir -p "$w/${dst}/$b"
+
+		set +e
+		env -C "$w" git ls-files -z | grep -zF "${dst}/$b/" | grep -zFv '/.' | env -C "$w" -u GIT_OPTIONAL_LOCKS xargs -r -0 git rm -f
+		find "$w/${dst}/$b/" -name '*.patch' -type f -exec rm -f {} +
+		set -e
+
+		git format-patch -N --subject-prefix='' --output-directory "$w/${dst}/$b" "${from}..$r"
+	else
+		echo >&2
+		git rebase --abort
+		echo >&2
+	fi
+
+	git switch -q --detach "${ref}"
+	git branch -D "$r"
+	echo >&2
+done
+
+cd "$w" ; rm -rf "$t"
+
+echo >&2
+echo 'put in debian/patches/series' >&2
+echo >&2
+find "${dst}/" -type f -name '*.patch' | sed -E 's#^debian/patches/##' | sort -V