[RX850V4] Interrupt

Is multiple interrupt servicing supported?

Yes, it is.
Multiple interrupt servicing occurs when an interrupt is acknowledged while another interrupt handler is being processed.

However, in the RX850, RX850Pro, or RX850, when an interrupt handler is started, its initial setting is "interrupts disabled," so interrupts must be enabled within the interrupt handler in order to acknowledge multiple interrupts.
In other words, the user must control whether interrupts are enabled (set via EI or the ena_int system call) or disabled (set via DI or the dis_int system call).