infra/rdn1edgex2: add user guide for rd-n1-edge dual-chip platform

Add the initial user guide for the RD-N1-Edge Dual-Chip platform
software stack. This version of the user guide points to documents that
provide information about how to obtain the platform software stack and
use the various features it provides.
Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Change-Id: I3668544148e33f93c3cad420ac5547f2493df974

docs/infra/rdn1edgex2/readme.rst

+RD-N1-Edge Dual-Chip platform software user guide
+=================================================
+
+.. contents::
+
+
+Introduction
+------------
+
+RD (Reference Design) is a collection of resources to provide a representative
+view of typical compute subsystems that can be designed and implemented using
+specific generations of Arm IP. RD-N1-Edge in particular is based on the
+following hardware configuration.
+
+- 8x `Neoverse N1 Cores <https://developer.arm.com/products/processors/neoverse/neoverse-n1>`_
+  with DynamIQ Shared Unit (DSU)
+- Dedicated L2 cache: 512KB per core
+- Shared L3 cache: 2MB per cluster
+- CMN-600 with CML option: 8MB System Level Cache and 16MB Snoop Filter
+- DMC-620 with 2xRDIMM DDR4-3200
+- Multiple AXI expansion ports for I/O Coherent PCIe, Ethernet, offload
+- Arm Cortex-M7 for System Control Processor (SCP) and
+  Manageability Control Processor (MCP)
+
+RD-N1-Edge dual-chip is a platform configuration in which two RD-N1-Edge
+platforms are connected through high speed CCIX link. The CCIX link is enabled
+by CMN600's Coherent Multichip Link. Such platforms are called RD-N1-Edge-Dual
+hereafter.
+
+This document is a user guide on how to setup, build and run the RD-N1-Edge-Dual
+software stack on the Fixed Virtual Platform.
+
+
+Setting up the Host Machine and downloading the software stack
+--------------------------------------------------------------
+
+Host Machine requirements and the necessary steps to be followed to sync the
+software stack are listed on '`Download sources`_' page.
+
+
+Obtaining the RD-N1-Edge-Dual Fast Model
+----------------------------------------
+
+The latest version of RD-N1-Edge-Dual Fast Model can be requested by sending a
+email to Arm at this email address: `support-connect@arm.com <mailto:support-connect@arm.com>`_.
+
+Follow the instruction in the installer and setup the FVP. Typically, the
+installer will ask to create a new folder in the home directory. You can either
+install the FVP in the home folder, or in the ``fastmodel/refinfra`` folder
+inside the workspace. If you would like to install in the ``fastmodel/refinfra``
+folder, when asked for the install location, provide the absolute path of the
+``fastmodel/refinfra``.
+
+
+Supported features
+------------------
+
+RD-N1-Edge-Dual platform software stack supports the following features.
+
+- `Busybox Boot`_.
+- `Buildroot Boot`_
+- `Linux Distribution Boot`_.
+- `UEFI Secure Boot`_
+
+Follow the links above for detailed information about the build and execute
+steps for each of the supported features.
+
+
+Release Tags
+------------
+
+Table below lists the release tags for the SGI-575 platform software stack and
+the corresponding SGI-575 FVP version that is recommended to be used along
+with the listed release tag. The summary of the changes introduced and tests
+validated in each release is listed in `change log`_.
+
++-----------------------+-----------------------------------+
+|     Release Tag       |    RD-N1-Edge-Dual FVP Version    |
++=======================+===================================+
+|  RD-INFRA-2021.02.24  |             11.13.43              |
++-----------------------+-----------------------------------+
+
+
+--------------
+
+*Copyright (c) 2021, Arm Limited. All rights reserved.*
+
+
+.. _Busybox Boot: docs/infra/common/busybox-boot.rst
+.. _Buildroot Boot: docs/infra/common/buildroot-boot.rst
+.. _Linux Distribution Boot: docs/infra/common/distro-boot.rst
+.. _UEFI Secure Boot: docs/infra/common/secure-boot.rst
+.. _Download sources: docs/infra/common/download-sources.rst
+.. _change log: docs/infra/change-log.rst