What are the functions of the diodes in this BLDC controller circuit?
To mimic what @jsotola already commented, D103 clamps the base of T102 at 1.25 VDC, so the emitter is fixed at 600 mV. This sinks a fixed 100 mA to ground for bias purposes.

This only happens when ETAT_MJP_PIC is high, else this bias is OFF, allowing ETAT_MJP to rise to its maximum voltage.

The voltage source for ETAT_MJP is not shown. The lack of voltages suggest this is part of a comm link.