diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 35aa87b96b71..e03d6ba5e5b4 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -145,7 +145,7 @@ struct uart_port {
 
 #define UPIO_PORT		(SERIAL_IO_PORT)	/* 8b I/O port access */
 #define UPIO_HUB6		(SERIAL_IO_HUB6)	/* Hub6 ISA card */
-#define UPIO_MEM		(SERIAL_IO_MEM)		/* 8b MMIO access */
+#define UPIO_MEM		(SERIAL_IO_MEM)		/* driver-specific */
 #define UPIO_MEM32		(SERIAL_IO_MEM32)	/* 32b little endian */
 #define UPIO_AU			(SERIAL_IO_AU)		/* Au1x00 and RT288x type IO */
 #define UPIO_TSI		(SERIAL_IO_TSI)		/* Tsi108/109 type IO */