DFU (Device Firmware Utility) is a host side (PC) utility and not residing on Edison
It is used for download firmware to device connected on USB.
On the Edison the boot components involved are
HW->Trusted Boot ROM -> IFWI ->Uboot -> Linux
Trusted Boot Rom which sits right on top of the HW: It is implemented as on-die silicon based ROM, and performs minimal hardware initialization and boots the IFWI firmware (Integrated Firmware)
IFWI (integrated firmware Image) - Contains firmware components required for initialization and operation of control units and accelerators within the SOC + first stage bootstrap
The first stage boot strap loads and runs the OS loader U-boot (second stage bootstrap to continue the booting of the Linux OS.
hope this helps in your understanding.
