About the relationship between U1 and U2 in teensy4.1

[Shun]

While studying the circuit diagram I discovered U1 (MIMXRT1062DVL6B) and U2 (MKL02Z32VFG4) are connected to each other.

Want to ask U1 and U2 effects and connect principle.

Is there any related theory?

 

[defragster]

U1 is the primary MCU 1062 processor.
U2 is the bootloader MCU that aids power up of the U1 1062 and is the chip that facilitates the "PJRC Teensy" Uploader process to program the U1 processor.