docs: a bunch of random updates

- Add a section about installing binary packages to the quickstart
  install page
- Remove the MacOS FAQ page; fold relevant content into other parts of
  the docs.
- Remove the redundant OPA networking page; its content was already
  included in the OFI networking page.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

Author: jsquyres

docs/faq/index.rst

@@ -24,6 +24,5 @@ that they are worth categorizing in an official way.
    large-clusters
 
    ompio
-   macos
 
    general-tuning

docs/faq/macos.rst

@@ -19,6 +19,40 @@ probably work in many environments.
    Developer's Guide </developers/index>` before attempting to build Open
    MPI. Really.
 
+Binary packages
+---------------
+
+Although the Open MPI community itself does not distribute binary
+packages for Open MPI, many downstream packagers do.
+
+For example, many Linux distributions include Open MPI packages
+|mdash| even if they are not installed by default.  You should consult
+the documentation and/or package list for your Linux distribution to
+see if you can use its built-in package system to install Open MPI.
+
+The MacOS package managers `Homebrew <https://brew.sh/>`_ and
+`MacPorts <https://macports.org/>`_ both offer binary Open MPI
+packages:
+
+.. code-block:: sh
+
+   # For Homebrew
+   shell$ brew install openmpi
+
+   # For MacPorts
+   shell$ port install openmpi
+
+.. important:: Binary packages may or may not include support for
+               features that are required on your platform (e.g., a
+               specific networking stack).  Or the binary packages
+               available to you may be older / out of date.  As such,
+               it may be better to build and install Open MPI from a
+               source tarball available from `the main Open MPI web
+               site <https://www.open-mpi.org/>`_.
+
+Building from source
+--------------------
+
 Open MPI uses a traditional ``configure`` script paired with ``make``
 to build.  Typical installs can be of the pattern:
 

docs/installing-open-mpi/quickstart.rst

@@ -22,7 +22,6 @@ build support for that library).
    ofi
    tcp
    shared-memory
-   opa
    ib-and-roce
    iwarp
    cuda

docs/networking/index.rst

@@ -78,7 +78,7 @@ For more information refer to the `Libfabric web site
 
 /////////////////////////////////////////////////////////////////////////
 
-Ompi-Path: How can the multi-rail settings be adjusted if multiple HFI (Host Fabric Interface) cards are installed on the system?
+Omni-Path: How can the multi-rail settings be adjusted if multiple HFI (Host Fabric Interface) cards are installed on the system?
 ---------------------------------------------------------------------------------------------------------------------------------
 
 Multi-Rail feature allows a process to use multiple HFIs to transfer a message