Other Parts Discussed in Thread: BQ21061
The Manual Reset Input (/MR) is pulled up internally to BAT. To drive the signal with a microcontroller (MCU) you can use a N-Channel mosfet (nMOS) to mimic a "press" action from the MCU. The below diagram shows the connection. Refer to the section 3 of the BQ21061 app note which includes an example of this application and is applicable to the BQ25120A as well.
BQ21061 SFF App Note Link: https://www.ti.com/lit/an/slua996/slua996.pdf