UART0_IRQ          15 kernel/plic.c    *(uint32 *)(PLIC + UART0_IRQ * 4) = 1;
UART0_IRQ          26 kernel/plic.c    *(uint32 *)PLIC_SENABLE(hart) = (1 << UART0_IRQ) | (1 << VIRTIO0_IRQ);
UART0_IRQ         198 kernel/trap.c      if (irq == UART0_IRQ) {