[U-Boot] Using U-boot command to write NAND flash

Please help, I am new to u-boot. The processor that we are using is AVR32 (AT32AP7000). U-Boot is a Boot Loader, its primary purpose is to load some operating system. Can we use the U-Boot to load our small application before loading the operating system (Linux)? Our small application will read a FPGA bit file from the NAND flash and configure the FPGA. U-Boot includes a basic interactive command interpreter, support for download over Ethernet and the capability to program the flash. Can we update the FPGA bit file (by programming NAND flash using U-boot command)? If yes, then which flash file system that U-boot uses to program the flash? and does that flasf file system take care of wear leveling in the NAND flash?

Thank you so much,