How to build usb otg download firmware package

Dear Banana Pi team, After compiling the BPI-M2U-bsp SDK( according to the steps in the BPI-M2Ultra_Compiler_SOP document, I can get two versions of firmware for Linux and tina (openwrt). Among them, the tina version firmware can be updated to emmc by using PhoenixSuit tools through the USB OTG interface on the bpi-m2-ultra board, but the Linux version system can only be updated to the on-board emmc by running a TF card.

I want to be able to compile firmware that is updated using USB via the PhoenixSuit tool, which will be very convenient. how should I do it?

Can anyone help me!

thank you very much!