mtd: nand: davinci: extend description of bindings

Extend bindings for davinci_nand driver to be more clear.
This is clarification only, without semantic changes.
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Taras Kondratiuk <taras@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

Documentation/devicetree/bindings/mtd/davinci-nand.txt

-* Texas Instruments Davinci NAND
+Device tree bindings for Texas instruments Davinci NAND controller
 
-This file provides information, what the device node for the
-davinci nand interface contain.
+This file provides information, what the device node for the davinci NAND
+interface contains.
+
+Documentation:
+Davinci DM646x - http://www.ti.com/lit/ug/sprueq7c/sprueq7c.pdf
 
 Required properties:
-- compatible: "ti,davinci-nand";
-- reg : contain 2 offset/length values:
-        - offset and length for the access window
-        - offset and length for accessing the aemif control registers
-- ti,davinci-chipselect: Indicates on the davinci_nand driver which
-                         chipselect is used for accessing the nand.
+
+- compatible:			"ti,davinci-nand"
+
+- reg:				Contains 2 offset/length values:
+				- offset and length for the access window.
+				- offset and length for accessing the AEMIF
+				control registers.
+
+- ti,davinci-chipselect:	number of chipselect. Indicates on the
+				davinci_nand driver which chipselect is used
+				for accessing the nand.
+				Can be in the range [0-3].
 
 Recommended properties :
-- ti,davinci-mask-ale: mask for ale
-- ti,davinci-mask-cle: mask for cle
-- ti,davinci-mask-chipsel: mask for chipselect
-- ti,davinci-ecc-mode: ECC mode valid values for davinci driver:
+
+- ti,davinci-mask-ale:		mask for ALE. Needed for executing address
+				phase. These offset will be added to the base
+				address for the chip select space the NAND Flash
+				device is connected to.
+				If not set equal to 0x08.
+
+- ti,davinci-mask-cle:		mask for CLE. Needed for executing command
+				phase. These offset will be added to the base
+				address for the chip select space the NAND Flash
+				device is connected to.
+				If not set equal to 0x10.
+
+- ti,davinci-mask-chipsel:	mask for chipselect address. Needed to mask
+				addresses for given chipselect.
+
+- ti,davinci-ecc-mode:		operation mode of the NAND ecc mode. ECC mode
+				valid values for davinci driver:
 				- "none"
 				- "soft"
 				- "hw"
+
 - ti,davinci-ecc-bits:		used ECC bits, currently supported 1 or 4.
-- ti,davinci-nand-buswidth: buswidth 8 or 16
-- ti,davinci-nand-use-bbt: use flash based bad block table support.
 
-nand device bindings may contain additional sub-nodes describing
-partitions of the address space. See partition.txt for more detail.
+- ti,davinci-nand-buswidth:	buswidth 8 or 16.
+
+- ti,davinci-nand-use-bbt:	use flash based bad block table support. OOB
+				identifier is saved in OOB area.
+
+Nand device bindings may contain additional sub-nodes describing partitions of
+the address space. See partition.txt for more detail. The NAND Flash timing
+values must be programmed in the chip select’s node of AEMIF
+memory-controller (see Documentation/devicetree/bindings/memory-controllers/
+davinci-aemif.txt).
 
 Example(da850 EVM ):
+
 nand_cs3@62000000 {
 	compatible = "ti,davinci-nand";
 	reg = <0x62000000 0x807ff