README: add some notes on flashing ITE and NPCX images

Add a couple notes on flashing ITE and NPCX images.

BUG=none
TEST=run the commands

Change-Id: I7eb17f596cf819b791f72fb1753a12b9e86c8975
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec-aic-tester/+/6169944
Reviewed-by: Keith Short <keithshort@chromium.org>
Commit-Queue: Fabio Baltieri <fabiobaltieri@google.com>
Tested-by: Fabio Baltieri <fabiobaltieri@google.com>

README.md

diff --git a/README.md b/README.md
index 1af8e83..a45898d 100644
--- a/README.md
+++ b/README.md
@@ -142,3 +142,26 @@
 ```
 west debug -r openocd
 ```
+
+## Flashing the AIC board
+
+### ITE
+
+```
+zmake build ite-aic
+itecomdbgr -f build/zephyr/ite-aic/output/ec.bin -d /dev/ttyACM1
+# reset the ec (ec reset)
+```
+
+### NPCX
+
+Assuming the tester shell is on /dev/ttyACM0 and the EC on /dev/ttyACM1, from
+the chroot in the EC directory:
+
+```
+zmake build npcx-aic
+# power on the ec (ec power on) enter bootloader mode (npcx_boot) on the tester shell
+uartupdatetool --port=ttyACM1 --baudrate=115200 --opr=wr --addr=0x200C3020 --file build/zephyr/npcx-aic/output/npcx_monitor.bin
+uartupdatetool --port=ttyACM1 --baudrate=115200 --opr=wr --auto --offset=0 --file build/zephyr/npcx-aic/output/ec.bin
+# reset the ec (ec reset)
+```