docs: mtd: spi-nor: drop obsolete info

The architecture description is obsolete, it no longer applies to
the current SPI NOR framework state, remove it.

Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Link: https://lore.kernel.org/r/20231124184902.1194235-3-tudor.ambarus@linaro.org
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

Author: ambarus

Documentation/driver-api/mtd/spi-nor.rst

@@ -2,68 +2,6 @@
 SPI NOR framework
 =================
 
-Part I - Why do we need this framework?
----------------------------------------
-
-SPI bus controllers (drivers/spi/) only deal with streams of bytes; the bus
-controller operates agnostic of the specific device attached. However, some
-controllers (such as Freescale's QuadSPI controller) cannot easily handle
-arbitrary streams of bytes, but rather are designed specifically for SPI NOR.
-
-In particular, Freescale's QuadSPI controller must know the NOR commands to
-find the right LUT sequence. Unfortunately, the SPI subsystem has no notion of
-opcodes, addresses, or data payloads; a SPI controller simply knows to send or
-receive bytes (Tx and Rx). Therefore, we must define a new layering scheme under
-which the controller driver is aware of the opcodes, addressing, and other
-details of the SPI NOR protocol.
-
-Part II - How does the framework work?
---------------------------------------
-
-This framework just adds a new layer between the MTD and the SPI bus driver.
-With this new layer, the SPI NOR controller driver does not depend on the
-m25p80 code anymore.
-
-Before this framework, the layer is like::
-
-                   MTD
-         ------------------------
-                  m25p80
-         ------------------------
-	       SPI bus driver
-         ------------------------
-	        SPI NOR chip
-
-After this framework, the layer is like::
-
-                   MTD
-         ------------------------
-              SPI NOR framework
-         ------------------------
-                  m25p80
-         ------------------------
-	       SPI bus driver
-         ------------------------
-	       SPI NOR chip
-
-With the SPI NOR controller driver (Freescale QuadSPI), it looks like::
-
-                   MTD
-         ------------------------
-              SPI NOR framework
-         ------------------------
-                fsl-quadSPI
-         ------------------------
-	       SPI NOR chip
-
-Part III - How can drivers use the framework?
----------------------------------------------
-
-The main API is spi_nor_scan(). Before you call the hook, a driver should
-initialize the necessary fields for spi_nor{}. Please see
-drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to spi-fsl-qspi.c
-when you want to write a new driver for a SPI NOR controller.
-
 How to propose a new flash addition
 -----------------------------------