docs: Add documentation of Arm 'imx25-pdk' board

Add brief documentation of the Arm 'imx25-pdk' board.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210722175229.29065-4-peter.maydell@linaro.org

MAINTAINERS

@@ -684,6 +684,7 @@ F: hw/watchdog/wdt_imx2.c
 F: include/hw/arm/fsl-imx25.h
 F: include/hw/misc/imx25_ccm.h
 F: include/hw/watchdog/wdt_imx2.h
+F: docs/system/arm/imx25-pdk.rst
 
 i.MX31 (kzm)
 M: Peter Maydell <peter.maydell@linaro.org>

docs/system/arm/imx25-pdk.rst

+NXP i.MX25 PDK board (``imx25-pdk``)
+====================================
+
+The ``imx25-pdk`` board emulates the NXP i.MX25 Product Development Kit
+board, which is based on an i.MX25 SoC which uses an ARM926 CPU.
+
+Emulated devices:
+
+- SD controller
+- AVIC
+- CCM
+- GPT
+- EPIT timers
+- FEC
+- RNGC
+- I2C
+- GPIO controllers
+- Watchdog timer
+- USB controllers

docs/system/target-arm.rst

@@ -95,6 +95,7 @@ undocumented; you can get a complete list by running
    arm/nrf
    arm/nseries
    arm/nuvoton
+   arm/imx25-pdk
    arm/orangepi
    arm/palm
    arm/raspi