+
+/* UART8250 Interrupt ID Register
+ * bit 0 Interrupt Pending 0 = true, 1 = false
+ * bit 2:1 ID of highest priority interrupt
+ * bit 7:3 zeroes
+ */
+#define IIR_NOPEND 0x1
+
+// Interrupt IDs
+#define IIR_MODEM 0x00 /* Modem Status (lowest priority) */
+#define IIR_TXID 0x02 /* Tx Data */
+#define IIR_RXID 0x04 /* Rx Data */
+#define IIR_LINE 0x06 /* Rx Line Status (highest priority)*/
+