Hello,
The INTC peripheral is designed to work like this: the reset value of the INTC_PSRn->PRC_SELN0 bitfield is 1, so all interrupts are enabled for core0 by default. Unfortunately, in SDK PA RTM 2.0.0 there is no way to automatically prevent this. You can only manually disable the interrupt for core0 before enabling the peripheral. This behavior is shown in the interrupt_control_multicore example.
However, the interrupt_manager driver has been recently rewritten and this issue is no longer present. When calling INT_SYS_EnableIRQ(irqNum), the driver will enable irqNum only for the current core and disable it for other cores. This feature should be included in the future SDK PA releases.
Best wishes,
Mihai Volmer