block, documentation: Explain the word 'segments'

Several block layer users who are not kernel developers do not know that
the word 'segment' refers to an element in a DMA scatter/gather list. Make
the block layer documentation easier to understand by stating explicitly
what the word 'segment' stands for.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Documentation/block/queue-sysfs.txt

@@ -98,8 +98,9 @@ This is the maximum number of kilobytes supported in a single data transfer.
 
 max_integrity_segments (RO)
 ---------------------------
-When read, this file shows the max limit of integrity segments as
-set by block layer which a hardware controller can handle.
+Maximum number of elements in a DMA scatter/gather list with integrity
+data that will be submitted by the block layer core to the associated
+block driver.
 
 max_sectors_kb (RW)
 -------------------
@@ -109,11 +110,12 @@ size allowed by the hardware.
 
 max_segments (RO)
 -----------------
-Maximum number of segments of the device.
+Maximum number of elements in a DMA scatter/gather list that is submitted
+to the associated block driver.
 
 max_segment_size (RO)
 ---------------------
-Maximum segment size of the device.
+Maximum size in bytes of a single element in a DMA scatter/gather list.
 
 minimum_io_size (RO)
 --------------------