Dual firmware devices like Linksys MX4200, MX4300, MX5300 and MX8500 use separate rootfs partition.
This option helps to keep all configuration during upgrade.
Signed-off-by: Paweł Owoc <frut3k7@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/14720
Signed-off-by: Robert Marko <robimarko@gmail.com>