Shutdown mode powers down the entire APU core. This mode is applicable to APU only. During shutdown, the entire processor state, including its caches, is completely lost; therefore, software is required to save all states before requesting the PMU to power down the APU core.
When a CPU is shutdown, it is expected that any interrupt from a peripheral that is associated with that CPU to initiate its power up; therefore, the interrupt lines to an APU core are also routed to the PMU interrupt controller, and are enabled when the APU core is powered down.
The Embedded Energy Management Interface EEMI API Reference Guide (UG1200) describe the APIs to invoke shutdown.
For more details, see this link to the “Platform Management Unit Programming Model” section in the Zynq UltraScale+ Device Technical Reference Manual (UG1085).