Index: kernel/arch/amd64/include/arch/interrupt.h
===================================================================
--- kernel/arch/amd64/include/arch/interrupt.h	(revision 0aee9b4c5afa08b0cd8ed8c15949d5a7208167d5)
+++ kernel/arch/amd64/include/arch/interrupt.h	(revision 30730e5e9bf741593943226bf927cba1283f2901)
@@ -53,4 +53,6 @@
 #define IRQ_KBD       1
 #define IRQ_PIC1      2
+/* NS16550 at COM1 */
+#define IRQ_NS16550   4
 #define IRQ_PIC_SPUR  7
 #define IRQ_MOUSE     12