Key takeaway from the PDF: SPMI supports a "collision detection" mechanism, allowing multiple masters (e.g., a modem and an AP) to coexist on the same bus.

No. SPMI is for power management devices. Use I2C for sensors, audio codecs, and touch controllers.

If you are a customer of Qualcomm, Texas Instruments, or Analog Devices, your FAE (Field Applications Engineer) may provide you with a licensed copy of the SPMI spec under NDA. This is common for large OEMs.