docs(imx8ulp): add imx8ulp platform

Add i.MX8ULP platform introduction.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: Idc16bcf5b23542f8a1f394a474309239ddcb9685

docs/plat/imx8ulp.rst

@@ -0,0 +1,69 @@
+NXP i.MX 8ULP
+==================
+
+i.MX 8ULP is part of the ULP family with emphasis on extreme low-power techniques
+using the 28 nm fully depleted silicon on insulator process. Like i.MX 7ULP,
+i.MX 8ULP continues to be based on asymmetric architecture.
+
+The i.MX 8ULP family of processors features NXP’s advanced implementation of the
+dual Arm Cortex-A35 cores alongside an Arm Cortex-M33. This combined architecture
+enables the device to run a rich operating system (such as Linux) on the Cortex-A35
+core and an RTOS (such as FreeRTOS) on the Cortex-M33 core. It also includes a Cadence
+Tensilica Fusion DSP for low-power audio and a HiFi4 DSP for advanced audio and machine
+learning applications.
+
+The design enables clean separation between two processing domains, where each has
+separate power, clocking and peripheral islands, but the bus fabric of each domain
+is tightly integrated for efficient communication. The part is streamlined to minimize
+pin count, enabling small packages and simple system integration. This microprocessor
+is intended for applications where efficiency and simple system integration is important.
+`i.MX8ULP Applications Processors`_.
+
+Boot Sequence
+-------------
+
+BootROM --> SPL --> BL31 --> BL33(u-boot) --> Linux kernel
+
+How to build
+------------
+
+Build Procedure
+~~~~~~~~~~~~~~~
+
+-  Prepare AARCH64 toolchain.
+
+- Get the ELE FW image from NXP linux SDK package
+
+-  Build SPL and u-boot firstly, and get binary images: u-boot-spl.bin,
+   u-boot.bin and dtb
+
+-  Build TF-A
+
+   Build bl31:
+
+   .. code:: shell
+
+       CROSS_COMPILE=aarch64-linux-gnu- make PLAT=<Target_SoC> bl31
+
+   Target_SoC should be "imx8ulp" for i.MX8ULP SoC.
+
+Deploy TF-A Images
+~~~~~~~~~~~~~~~~~~
+
+TF-A binary(bl31.bin), u-boot-spl.bin u-boot.bin, ELE FW image are combined
+together to generate a binary file called flash.bin, the imx-mkimage tool is
+used to generate flash.bin, and flash.bin needs to be flashed into SD card
+with certain offset for BOOT ROM.
+
+Reference Documentation
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Details on how to prepare, generate & deploy the boot image be found in following documents:
+
+- i.MX Linux User's Guide
+  `link <https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applications-processors:IMXLINUX>`__
+- i.MX Linux Reference Manual
+  `link <https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applications-processors:IMXLINUX>`__
+
+.. _i.MX8ULP Applications Processors: https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-processors/i-mx-8-applications-processors/i-mx-8ulp-applications-processor-family:i.MX8ULP
+

docs/plat/index.rst

@@ -27,6 +27,7 @@ Platform Ports
    warp7
    imx8
    imx8m
+   imx8ulp
    imx9
    npcm845x
    nxp/index