layerscape: add a README for build and deployment

Added a README for layerscape targets build and deployment.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>

target/linux/layerscape/README

@@ -0,0 +1,151 @@
+
+Layerscape Quick Start
+
+1. Layerscape target support
+----------------------------
+* ARMv8 64-bit
+  LS1012ARDB LS1012AFRDM LS1043ARDB LS1046ARDB LS1088ARDB LS2088ARDB
+
+* ARMv8 32-bit
+  LS1012ARDB LS1012AFRDM LS1043ARDB LS1046ARDB
+
+
+2. Build
+--------
+
+2.1 make menuconfig
+-------------------
+* For single device
+
+  Target System:   "NXP Layerscape".
+  Subtarget:       "ARMv8 64-bit based boards" or "ARMv8 32-bit based boards"
+  Target Profile:  (select device you want to build)
+
+  For example, build firmware for 64-bit ls1043ardb.
+  +---------------------------------------------+
+  | Target System (NXP Layerscape)  --->        |
+  |---------------------------------------------|
+  | Subtarget (ARMv8 64-bit based boards)  ---> |
+  |---------------------------------------------|
+  | Target Profile (ls1043ardb-armv8_64b)  ---> |
+  +---------------------------------------------+
+
+* For multiple devices
+
+  Target System:   "NXP Layerscape".
+  Subtarget:       "ARMv8 64-bit based boards" or "ARMv8 32-bit based boards"
+  Target Profile:  "Multiple devices"
+  Target Devices:  (select devices you want to build)
+
+  For example, build firmware for all 64-bit devices.
+  Target Devices  --->
+  +-----------------------------------------------------------------+
+  | [*] Enable all profiles by default                              |
+  |-----------------------------------------------------------------|
+  | [ ] Use a per-device root filesystem that adds profile packages |
+  |-----------------------------------------------------------------|
+  | [*] ls1012afrdm-armv8_64b  ----                                 |
+  |-----------------------------------------------------------------|
+  | [*] ls1012ardb-armv8_64b  ----                                  |
+  |-----------------------------------------------------------------|
+  | [*] ls1043ardb-armv8_64b  ----                                  |
+  |-----------------------------------------------------------------|
+  | [*] ls1046ardb-armv8_64b  ----                                  |
+  |-----------------------------------------------------------------|
+  | [*] ls1088ardb-armv8_64b  ----                                  |
+  |-----------------------------------------------------------------|
+  | [*] ls2088ardb-armv8_64b  ----                                  |
+  +-----------------------------------------------------------------+
+
+  Note: per-device root filesystem hasn't been supported for now.
+
+2.2 make (or make -j<n>)
+------------------------
+
+2.3 Final firmware
+------------------
+Final firmware would be in bin/targets/layerscape/<subtarget>/, and
+named as lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin.
+
+
+3. Program firmware to NOR/QSPI flash
+-------------------------------------
+* LS1043ARDB (NOR flash)
+
+  Start up from bank0, and program firmware to bank4 with below commands.
+  Switch to bank4 to start up LEDE.
+
+  => tftp a0000000 lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin
+  => protect off all
+  => erase 64000000 +$filesize
+  => cp.b a0000000 64000000 $filesize
+  => cpld reset altbank
+
+* LS2088ARDB (NOR flash)
+
+  Start up from bank0, and program firmware to bank4 with below commands.
+  Switch to bank4 to start up LEDE.
+
+  => tftp a0000000 lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin
+  => protect off all
+  => erase 584000000 +$filesize
+  => cp.b a0000000 584000000 $filesize
+  => qix altbank
+
+* LS1012ARDB (QSPI flash)
+
+  Start up from bank1, and program firmware to bank2 with below commands.
+  Switch to bank2 to start up LEDE.
+
+  => tftp a0000000 lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin
+  => i2c mw 0x24 0x7 0xfc;i2c mw 0x24 0x3 0xf5
+  => sf probe 0:0
+  => sf erase 0 +$filesize
+  => sf write a0000000 0 $filesize
+  => reset
+
+* LS1012AFRDM (QSPI flash)
+
+  LS1012AFRDM board only has one bank. Start up board, and program firmware
+  with below commands. Reset to start up LEDE.
+
+  => tftp 96000000 lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin
+  => sf probe 0:0
+  => sf erase 0 +$filesize
+  => sf write 96000000 0 $filesize
+  => reset
+
+* LS1046ARDB (QSPI flash)
+
+  Start up from bank1, and program firmware to bank2 with below commands.
+  Switch to bank2 to start up LEDE.
+
+  => tftp a0000000 lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin
+  => sf probe 0:1
+  => sf erase 0 +$filesize
+  => sf write a0000000 0 $filesize
+  => cpld reset altbank
+
+* LS1088ARDB (QSPI flash)
+
+  Start up from bank0, and program firmware to bank1 with below commands.
+  Switch to bank1 to start up LEDE.
+
+  => tftp a0000000 lede-layerscape-<subtarget>-<device>-squashfs-firmware.bin
+  => sf probe 0:1
+  => sf erase 0 +$filesize
+  => sf write a0000000 0 $filesize
+  => qix altbank
+
+  Note: old version u-boot of ls1088ardb may use below commands to switch to
+  bank1 instead of 'qix altbank'.
+  => i2c mw 66 50 20;i2c mw 66 10 20;i2c mw 66 10 21
+
+
+4. Other references and sources
+-------------------------------
+- NXP LSDK site: https://lsdk.github.io/
+
+- NXP LSDK github: https://github.com/qoriq-open-source
+
+- LEDE documentation: https://lede-project.org/docs/start