EEPROM: Add a README file

Documentation/README.html

@@ -260,6 +260,8 @@
  |   |   |   `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/configs/zp214xpa/README.txt"><b><i>README.txt</i></b></a>
  |   |   `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/configs/README.txt"><b><i>README.txt</i></b></a>
  |   |- drivers/
+ |   |   |- eeprom/
+ |   |   |   `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/drivers/eeprom/README.txt"><b><i>README.txt</i></b></a>
  |   |   |- lcd/
  |   |   |   `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/drivers/lcd/README.txt"><b><i>README.txt</i></b></a>
  |   |   |- mtd/

README.txt

@@ -1216,6 +1216,8 @@ nuttx
  |   |   `- README.txt
  |   `- README.txt
  |- drivers/
+ |   |- eeprom/
+ |   |   `- README.txt
  |   |- lcd/
  |   |   `- README.txt
  |   |- mtd/

drivers/eeprom/spi_xx25xx.c

@@ -33,7 +33,7 @@
  *
  ****************************************************************************/
 
-/* This is a driver for SPI EEPROMs that uses the same commands as the
+/* This is a driver for SPI EEPROMs that use the same commands as the
  * 25AA160.
  *
  * Write time 5ms, 6ms for 25xx1025 (determined automatically with polling)

drivers/mtd/README.txt

@@ -8,6 +8,20 @@ MTD README
 
   See include/nuttx/mtd/mtd.h for additional information.
 
+EEPROM
+======
+  EEPROMs are a form of Memory Technology Device (MTD).  EEPROMs are non-
+  volatile memory like FLASH, but differ in underlying memory technology and
+  differ in usage in many respects:  They may not be organized into blocks
+  (at least from the standpoint of the user) and it is not necessary to
+  erase the EEPROM memory before re-writing it.  In addition, EEPROMs tend
+  to be much smaller than FLASH parts, usually only a few kilobytes vs
+  megabytes for FLASH.  EEPROM tends to be used to retain a small amount of
+  device configuration information; FLASH tends to be used for program or
+  massive data storage. For these reasons, it may not be convenient to use
+  the more complex MTD interface but instead use the simple character
+  interface provided by the EEPROM drivers.  See drivers/eeprom.
+
 NAND MEMORY
 ===========