doc: add supported platforms list

Author: rvagg

BUILDING.md

@@ -9,20 +9,78 @@ If you consistently can reproduce a test failure, search for it in the
 file a new issue.
 
 
+## Supported platforms
+
+This list of supported platforms is current as of the branch / release to which it is attached.
+
+### Input
+
+We rely on a few dependencies that _makes us who we are—most importantly V8 and libuv. We therefore need to adopt their supported platforms and potentially add to their lists based on test and/or release coverage.
+
+### Strategy
+
+Support is divided into three tiers:
+
+* **Tier 1**: Full test coverage and maintenance by the Node.js core team and the broader community.
+* **Tier 2**: Full test coverage but more limited maintenance, often provided by the vendor of the platform. 
+* **Experimental**: Known to compile but not necessarily reliably or with a full passing test suite. These are often working to be promoted to Tier 2 but are not quite ready. There is at least one individual actively providing maintenance and the team is striving to broaden quality and reliability of support.
+
+### Supported platforms
+
+|  System      | Support type | Version                          | Architectures        | Notes            |
+|--------------|--------------|----------------------------------|----------------------|------------------|
+| GNU/Linux    | Tier 1       | kernel >= 2.6.18, glibc >= 2.5   | x86, x64, arm, arm64 |                  | 
+| macOS        | Tier 1       | >= 10.10                         | x64                  |                  |
+| Windows      | Tier 1       | >= Windows 7 or >= Windows2008R2 | x86, x64             |                  |
+| SmartOS      | Tier 2       | = 14                             | x86, x64             |                  |
+| FreeBSD      | Tier 2       | >= 10                            | x64                  |                  |
+| GNU/Linux    | Tier 2       | kernel >= 4.2.0, glibc >= 2.19   | ppc64be              |                  |
+| GNU/Linux    | Tier 2       | kernel >= 3.13.0, glibc >= 2.19  | ppc64le              |                  |
+| AIX          | Tier 2       | >= 6.1                           | ppc64be              |                  |
+| GNU/Linux    | Tier 2       | kernel >= 3.10, glibc >= 2.17    | s390x                |                  |
+| macOS        | Experimental | >= 10.8 < 10.10                  | x64                  | no test coverage |
+| SmartOS      | Experimental | >= 15                            | x86, x64             |                  |
+| Linux (musl) | Experimental | musl >= 1.0                      | x64                  |                  |
+
+### Supported toolchains
+
+Depending on host platform, the selection of toolchains may vary.
+
+#### Unix
+
+* GCC 4.8 or newer
+* Clang 3.4.1 or newer
+
+#### Windows
+
+* Building Node: Visual Studio 2015¹ or Visual C++ Build Tools 2015 or newer
+* Building native add-ons: Visual Studio 2013 or Visual C++ Build Tools 2015 or newer
+
+### Shared libraries & dependencies
+
+Node.js intends to support building against shared representations of dependencies found found in the [*deps*][./deps/] directory.
+
+
+## Building Node.js on supported platforms
+
 ### Unix / OS X
 
 Prerequisites:
 
 * `gcc` and `g++` 4.8 or newer, or
-* `clang` and `clang++` 3.4 or newer
+* `clang` and `clang++` 3.4.1 or newer
 * Python 2.6 or 2.7
 * GNU Make 3.81 or newer
 
 On OS X, you will also need:
 * [Xcode](https://developer.apple.com/xcode/download/)
+<<<<<<< HEAD
   * You also need to install the `Command Line Tools` via Xcode. You can find
+=======
+  - You also need to install the `Command Line Tools` via Xcode. You can find
+>>>>>>> doc: add supported platforms list
     this under the menu `Xcode -> Preferences -> Downloads`
-  * This step will install `gcc` and the related toolchain containing `make`
+  - This step will install `gcc` and the related toolchain containing `make`
 
 * After building, you may want to setup [firewall rules](tools/macosx-firewall.sh)
 to avoid popups asking to accept incoming network connections when running tests:

README.md

@@ -132,7 +132,7 @@ the binary verification command above.
 ## Building Node.js
 
 See [BUILDING.md](BUILDING.md) for instructions on how to build
-Node.js from source.
+Node.js from source along with a list of officially supported platforms.
 
 ## Security