misc/at25, dt: Improve at25 SPI eeprom device tree bindings.

Commit 002176db (misc: at25: Parse dt settings) added device tree
bindings the differ significantly in style from the I2C EEPROM
bindings and don't seem well vetted.  Here I deprecate (but still
support) the "at25,*" properties, and add what I hope is a better
alternative.  These new bindings also happen to be deployed in the
field and were previously submitted for consideration here:

https://lists.ozlabs.org/pipermail/devicetree-discuss/2012-May/015556.html

The advantages of the new bindings are that they are similar to the
I2C EEPROMs and they don't conflate read-only and the address width
modes in a binary encoded blob.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: Alexandre Pereira da Silva <aletes.xgr@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michael Hennerich <michael.hennerich@analog.com>
Cc: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/misc/at25.txt

@@ -1,21 +1,35 @@
-Atmel AT25 eeprom
+EEPROMs (SPI) compatible with Atmel at25.
 
 Required properties:
 - compatible : "atmel,at25".
 - reg : chip select number
 - spi-max-frequency : max spi frequency to use
+- pagesize : size of the eeprom page
+- size : total eeprom size in bytes
+- address-width : number of address bits (one of 8, 16, or 24)
 
+Optional properties:
+- spi-cpha : SPI shifted clock phase, as per spi-bus bindings.
+- spi-cpol : SPI inverse clock polarity, as per spi-bus bindings.
+- read-only : this parameter-less property disables writes to the eeprom
+
+Obsolete legacy properties are can be used in place of "size", "pagesize",
+"address-width", and "read-only":
 - at25,byte-len : total eeprom size in bytes
 - at25,addr-mode : addr-mode flags, as defined in include/linux/spi/eeprom.h
 - at25,page-size : size of the eeprom page
 
-Examples:
-at25@0 {
-	compatible = "atmel,at25";
-	reg = <0>
-	spi-max-frequency = <5000000>;
+Additional compatible properties are also allowed.
 
-	at25,byte-len = <0x8000>;
-	at25,addr-mode = <2>;
-	at25,page-size = <64>;
-};
+Example:
+	at25@0 {
+		compatible = "atmel,at25", "st,m95256";
+		reg = <0>
+		spi-max-frequency = <5000000>;
+		spi-cpha;
+		spi-cpol;
+
+		pagesize = <64>;
+		size = <32768>;
+		address-width = <16>;
+	};