board: rockchip: Add FriendlyElec NanoPi R2S Plus

The FriendlyElec NanoPi R2S Plus is a single-board computer based on
Rockchip RK3328 SoC. It features e.g. 1 GB DDR4 RAM, 32 GB eMMC,
SD-card, 2x GbE LAN, optional M.2 SDIO Wi-Fi and 2x USB 2.0 host.

Features tested on a NanoPi R2S Plus 2309:
- SD-card boot
- eMMC boot
- Ethernet
- USB gadget
- USB host

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/board/rockchip/evb_rk3328/MAINTAINERS b/board/rockchip/evb_rk3328/MAINTAINERS
index 8f619e5..5f81be5 100644
--- a/board/rockchip/evb_rk3328/MAINTAINERS
+++ b/board/rockchip/evb_rk3328/MAINTAINERS
@@ -28,6 +28,12 @@
 F:      arch/arm/dts/rk3328-nanopi-r2s-u-boot.dtsi
 F:      arch/arm/dts/rk3328-nanopi-r2s.dts
 
+NANOPI-R2S-PLUS-RK3328
+M:      Jonas Karlman <jonas@kwiboo.se>
+S:      Maintained
+F:      configs/nanopi-r2s-plus-rk3328_defconfig
+F:      arch/arm/dts/rk3328-nanopi-r2s-plus-u-boot.dtsi
+
 ORANGEPI-R1-PLUS-RK3328
 M:      Tianling Shen <cnsztl@gmail.com>
 S:      Maintained