Updates to install and tests

Includes CAD suite info and details on the OSS CAD suite nightly build targets.
Instructions for building from source, largely based on the readme but with some minor modifications.
Tests are still WIP, but we replaced the old test suites with a brief comment on the github workflow tests.  Still needs more on the tests themselves and how to run them locally.
Also an extra todo on the index page.

docs/source/getting_started/installation.rst

@@ -1,14 +1,148 @@
 Installation
 ------------
 
-.. todo:: update and finish installation instructions
+This document will guide you through the process of installing Yosys.
+
+CAD suite(s)
+~~~~~~~~~~~~
+
+Yosys is part of the `Tabby CAD Suite
+<https://www.yosyshq.com/tabby-cad-datasheet>`_ and the `OSS CAD Suite
+<https://github.com/YosysHQ/oss-cad-suite-build>`_! The easiest way to use yosys
+is to install the binary software suite, which contains all required
+dependencies and related tools.
+
+* `Contact YosysHQ <https://www.yosyshq.com/contact>`_ for a `Tabby CAD Suite
+  <https://www.yosyshq.com/tabby-cad-datasheet>`_ Evaluation License and
+  download link
+* OR go to https://github.com/YosysHQ/oss-cad-suite-build/releases to download
+  the free OSS CAD Suite
+* Follow the `Install Instructions on GitHub
+  <https://github.com/YosysHQ/oss-cad-suite-build#installation>`_
+
+Make sure to get a Tabby CAD Suite Evaluation License if you need features such
+as industry-grade SystemVerilog and VHDL parsers!
+
+For more information about the difference between Tabby CAD Suite and the OSS
+CAD Suite, please visit https://www.yosyshq.com/tabby-cad-datasheet
+
+Many Linux distributions also provide Yosys binaries, some more up to date than
+others. Check with your package manager!
+
+Targeted architectures
+^^^^^^^^^^^^^^^^^^^^^^
+
+The `OSS CAD Suite`_ releases `nightly builds`_ for the following architectures:
+
+- linux-x64 |linux-x64|
+   - Most personal Linux based computers
+
+- darwin-x64 |darwin-x64|
+   - macOS 10.14 or later with Intel CPU
+
+- darwin-arm64 |darwin-arm64|
+   - macOS 11.00 or later with M1 CPU
+
+- windows-x64 |windows-x64|
+   - Targeted for Windows 10 and 11, but older 64-bit version of Windows 7, 8,
+     or 8.1 should work
+
+- linux-arm |linux-arm|
+- linux-arm64 |linux-arm64|
+- linux-riscv64 (untested) |linux-riscv64|
+
+.. _OSS CAD Suite: https://github.com/YosysHQ/oss-cad-suite-build
+.. _nightly builds: https://github.com/YosysHQ/oss-cad-suite-build/releases/latest
+
+.. |linux-x64| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/linux-x64.yml/badge.svg
+.. |darwin-x64| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/darwin-x64.yml/badge.svg
+.. |darwin-arm64| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/darwin-arm64.yml/badge.svg
+.. |windows-x64| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/windows-x64.yml/badge.svg
+.. |linux-arm| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/linux-arm.yml/badge.svg
+.. |linux-arm64| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/linux-arm64.yml/badge.svg
+.. |linux-riscv64| image:: https://github.com/YosysHQ/oss-cad-suite-build/actions/workflows/linux-riscv64.yml/badge.svg
+
+Building from source
+~~~~~~~~~~~~~~~~~~~~
+
+Refer to the `readme`_ for the most up-to-date install instructions.
+
+.. _readme: https://github.com/YosysHQ/yosys#building-from-source
 
 Supported platforms
-~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^
+
+The following platforms are supported and regularly tested:
+
+- Linux
+- macOS
+
+Other platforms which may work, but instructions may not be up to date and are
+not regularly tested:
+
+- FreeBSD
+- WSL
+- Windows with (e.g.) Cygwin
+
+Build prerequisites
+^^^^^^^^^^^^^^^^^^^
+
+A C++ compiler with C++11 support is required as well as some standard tools
+such as GNU Flex, GNU Bison, Make, libffi, and Python3.6 or later.  Some
+additional tools: readline, Tcl and zlib; are optional but enabled by default
+(see ``ENABLE_*`` settings in Makefile). Xdot (graphviz) is optional unless
+using the :cmd:ref:`show` command to display schematics.
+
+.. 
+   unclear if libffi is required now or still optional
+   readme says optional, but I can't find a corresponding ENABLE_*
+
+Installing all prerequisites for Ubuntu 20.04:
+
+.. code:: console
+
+   sudo sudo apt-get install build-essential clang bison flex \
+      libreadline-dev gawk tcl-dev libffi-dev git make \
+      graphviz xdot pkg-config python3 libboost-system-dev \
+      libboost-python-dev libboost-filesystem-dev zlib1g-dev
+
+Installing all prerequisites for macOS 11 (with Homebrew):
+
+.. code:: console
+
+   brew install bison flex gawk libffi git graphviz \
+      pkg-config python3 tcl-tk xdot bash boost-python3
+
+Running the build system
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+To configure the build system to use a specific compiler, use one of the
+following:
+
+.. code:: console
+
+   make config-clang
+   make config-gcc
+
+Then, simply run ``make`` in this directory.
+
+.. code:: console
+   
+   make
+   sudo make install
+
+Note that this also downloads, builds, and installs ABC (using yosys-abc as the
+executable name).
+
+.. seealso:: 
+
+   Refer to :doc:`/test_suites` for details on testing Yosys once compiled.
 
 Source tree and build system
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+.. todo:: check if source tree/build system details need updating
+
 The Yosys source tree is organized into the following top-level
 directories: