resources: Document IORESOURCE_IO

Help clarify that this is specifically for PCI/ISA I/O ports and not for
any other similar thing.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NHaojian Zhuang <haojian.zhuang@gmail.com>
Tested-by: NHaojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

include/linux/ioport.h

@@ -29,7 +29,7 @@ struct resource {
 #define IORESOURCE_BITS		0x000000ff	/* Bus-specific bits */
 
 #define IORESOURCE_TYPE_BITS	0x00001f00	/* Resource type */
-#define IORESOURCE_IO		0x00000100
+#define IORESOURCE_IO		0x00000100	/* PCI/ISA I/O ports */
 #define IORESOURCE_MEM		0x00000200
 #define IORESOURCE_REG		0x00000300	/* Register offsets */
 #define IORESOURCE_IRQ		0x00000400