This is a minimal version of the System.BB.Interrupts interface available in Ravenscar. Close enough that these packages can be used interchangably for the purposes of the RP drivers.
procedure Attach_Handler
   (Handler : not null Interrupt_Handler;
    Id      : Interrupt_ID;
    Prio    : Interrupt_Priority)
type Interrupt_Handler     is access procedure;
subtype Interrupt_ID       is Cortex_M.NVIC.Interrupt_ID;
subtype Interrupt_Priority is System.Interrupt_Priority;
procedure Interrupt_Request_Handler