Interrupt Processor Targets Registers
Summary of the implementation defined features of the ICDIPTRn.
For systems that support only one Cortex®‑A9 processor, all these registers read as zero, and writes are ignored. The single Cortex‑A9 processor is always set as the target of any interruption.
For systems that support two or more Cortex‑A9 processors, if the Processor Target field is set to 0 for a specific SPI, then this interrupt cannot be set pending through the hardware pins, nor by a write to the Set-Pending register.