Add Subzero documentation.

README.md

@@ -38,6 +38,21 @@ Changes are uploaded to Gerrit by performing:
 
     git push origin HEAD:refs/for/master
 
+Third-Party Dependencies
+------------------------
+
+The [third_party](third_party/) directory contains projects which originated outside of SwiftShader:
+
+[LLVM](third_party/LLVM/) contains an outdated and diverged copy of the [LLVM](http://llvm.org/) compiler framework. Until further notice, maintenance fixes can be made directly in the SwiftShader repository.
+
+[subzero](third_party/subzero/) contains a fork of the [Subzero](https://chromium.googlesource.com/native_client/pnacl-subzero/) project. It is part of Google Chrome's (Portable) [Native Client](https://developer.chrome.com/native-client) project. Its authoritative source is at [https://chromium.googlesource.com/native_client/pnacl-subzero/](https://chromium.googlesource.com/native_client/pnacl-subzero/). The fork was made using [git-subtree](https://github.com/git/git/blob/master/contrib/subtree/git-subtree.txt) to include all of Subzero's history, and until further notice it should **not** diverge from the upstream project. Contributions must be tested using the [README](third_party/subzero/docs/README.rst) instructions, reviewed at [https://chromium-review.googlesource.com](https://chromium-review.googlesource.com/q/project:native_client%252Fpnacl-subzero), and then pulled into the SwiftShader repository.
+
+[llvm-subzero](third_party/llvm-subzero/) contains a minimized set of LLVM dependencies of the Subzero project.
+
+[PowerVR_SDK](third_party/PowerVR_SDK/) contains a subset of the [PowerVR Graphics Native SDK](https://github.com/powervr-graphics/Native_SDK) for running several sample applications.
+
+[googletest](third_party/googletest/) contains the [Google Test](https://github.com/google/googletest) project, as a Git submodule. It is used for running unit tests for Chromium, and Reactor unit tests. Run `git submodule update --init` to obtain/update the code. Any contributions should be made upstream.
+
 Documentation
 -------------
 

docs/Index.md

@@ -20,7 +20,7 @@ The Renderer layer generates specialized processing routines for draw calls and
 
 Reactor is an embedded language for C++ to dynamically generate code in a WYSIWYG fashion. It allows to specialize the processing routines for the state and shaders used by each draw call. Its syntax closely resembles C and shading languages, to make the code generation easily readable.
 
-The JIT layer is a run-time compiler, such as LLVM's JIT. Reactor records its operations in an in-memory intermediate form which can be materialized by the JIT into a function which can be called directly.
+The JIT layer is a run-time compiler, such as [LLVM](http://llvm.org/)'s JIT. Reactor records its operations in an in-memory intermediate form which can be materialized by the JIT into a function which can be called directly.
 
 Design
 ------