bmips: add subtargets for each SoC

BMIPS is a generic arch that can be used for multiple Broadcom SoCs, each one
with its own specific drivers, so instead of having a huge kernel supporting
all of them, let's switch to a subtarget per SoC like other OpenWrt targets.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

target/linux/bmips/base-files/lib/upgrade/cfe-jffs2-nand.sh

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+cfe_jffs2_nand_upgrade() {
+	local tar_file="$1"
+	local kernel_mtd="$(find_mtd_index $CI_KERNPART)"
+
+	if [ -z "$kernel_mtd" ]; then
+		echo "$CI_KERNPART partition not found"
+		return 1
+	fi
+
+	local board_dir=$(tar tf $tar_file | grep -m 1 '^sysupgrade-.*/$')
+	board_dir=${board_dir%/}
+
+	local kernel_length=$(tar xf $tar_file ${board_dir}/kernel -O | wc -c 2> /dev/null)
+	local rootfs_length=$(tar xf $tar_file ${board_dir}/root -O | wc -c 2> /dev/null)
+
+	if [ "$kernel_length" = 0 ]; then
+		echo "kernel cannot be empty"
+		return 1
+	fi
+
+	flash_erase -j /dev/mtd${kernel_mtd} 0 0
+	tar xf $tar_file ${board_dir}/kernel -O | nandwrite /dev/mtd${kernel_mtd} -
+
+	local rootfs_type="$(identify_tar "$tar_file" ${board_dir}/root)"
+
+	nand_upgrade_prepare_ubi "$rootfs_length" "$rootfs_type" "0" "0"
+
+	local ubidev="$( nand_find_ubi "$CI_UBIPART" )"
+
+	local root_ubivol="$(nand_find_volume $ubidev $CI_ROOTPART)"
+	tar xf $tar_file ${board_dir}/root -O | \
+		ubiupdatevol /dev/$root_ubivol -s $rootfs_length -
+
+	nand_do_upgrade_success
+}