adrv936x: Add u-boot-env page as orphan

docs/solutions/reference-designs/adrv9361z7035/u-boot-env-fix.rst

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+:orphan:
+
+.. imported from: https://wiki.analog.com/resources/eval/user-guides/adrv936x_rfsom/u-boot-env-fix
+
+.. _adrv936x u-boot-env-fix:
+
+ADRV9361/ADRV9364 U-Boot Environment Fix
+=========================================
+
+Some ADRV9361/ADRV9364 boards left the factory with the u-boot environment
+variable flash partition not properly initialized. This causes the board to
+remain stuck at the u-boot prompt instead of booting normally. This is a
+firmware-only issue and does not affect hardware quality.
+
+How to Check if Your Board Has This Issue
+-----------------------------------------
+
+Connect a MicroUSB cable to the UART port and power on the board. If the board
+is affected, it will stop at the ``Zynq>`` prompt instead of booting into Linux:
+
+.. code-block::
+
+   Model: Zynq Zed Development Board
+   Board: Xilinx Zynq
+   Silicon: v3.1
+   DRAM:  ECC disabled 512 MiB
+   MMC:   sdhci@e0100000: 0 (SD)
+   SF: Detected n25q256a with page size 256 Bytes, erase size 4 KiB, total 32 MiB
+   In:    serial@e0001000
+   Out:   serial@e0001000
+   Err:   serial@e0001000
+   Net:   ZYNQ GEM: e000b000, phyaddr 0, interface rgmii-id
+   eth0: ethernet@e000b000
+   Zynq>
+
+Instructions for Resetting the Environment
+------------------------------------------
+
+Find the MAC address on the sticker on your board (format: ``00:05:f7:80:26:ef``):
+
+.. image:: images/adrv936x_mac_addr_sticker.jpg
+   :alt: MAC address sticker on the ADRV9361/ADRV9364 board
+   :width: 400
+
+Then run the following commands at the ``Zynq>`` prompt, substituting your
+board's MAC address:
+
+.. code-block::
+
+   Zynq> env default -a
+   Zynq> setenv ethaddr "00:05:f7:80:26:ef"
+   Zynq> saveenv
+   Zynq> reset
+
+The board will reset and boot normally.
+
+If ``saveenv`` Returns an Error (Flash Partition Locked)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Boot into Linux first by running:
+
+.. code-block::
+
+   Zynq> env default -a
+   Zynq> run sdboot
+
+Once booted into Linux, unlock and erase the flash partition:
+
+.. code-block::
+
+   root@analog:~# flash_unlock /dev/mtd1
+   root@analog:~# flash_erase /dev/mtd1 0 0
+   root@analog:~# reboot
+
+When the board reboots, press any key when prompted with
+``Hit any key to stop autoboot`` to return to the u-boot prompt. Then repeat
+the standard fix above.
+
+Other Support
+-------------
+
+If the issue persists, contact Analog Devices support via
+:ez:`EngineerZone <community/linux-device-drivers/linux-software-drivers>`.