docs: add new top-level docs builder that builds docs for a single chip

docs/include_build_file.py

@@ -0,0 +1,18 @@
+import os.path
+from docutils.parsers.rst import Directive, directives
+from docutils.parsers.rst.directives.misc import Include as BaseInclude
+from sphinx.util.docutils import SphinxDirective
+
+class IncludeBuildFile(BaseInclude, SphinxDirective):
+    """
+    Like the standard "Include" directive, but relative to the app
+    build directory
+    """
+    def run(self):
+        abspath = os.path.join(self.env.config.build_dir, self.arguments[0])
+        self.arguments[0] = abspath
+        self.env.note_included(abspath)
+        return super(IncludeBuildFile, self).run()
+
+def setup(app):
+      directives.register_directive('include-build-file', IncludeBuildFile)