Is possible to boot OpenWrt directly from the SPI NOR Flash?

As in the topic.
Is possible to boot OpenWrt directly from the SPI NOR Flash on NanoPi R2S ?
Thanks to Spd666 https://forum.openwrt.org/t/is-there-any-dev-working-on-the-nanopi-r2s/58730/90 we can boot U-Boot on NanoPi from SPI flash, but OpenWrt has to be on SD card.
How to boot OpenWrt without SD card?