README: update code search links

BUG=None
TEST=read the docs

Change-Id: I6dba3183fa69c823d32d43e654b3c82a6f8ff826
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2685279
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/README.md b/README.md
index 24f1a6c..18c4928 100644
--- a/README.md
+++ b/README.md
@@ -28,11 +28,25 @@
 
 ## Directory Overview
 
-You can use [Code Search](https://cs.corp.google.com/) to lookup things in
-Chromite or ChromeOS in general. You can add a ChromeOS filter to only show
-files from CrOS repositories by going to
-[CS Settings](https://cs.corp.google.com/settings/) and adding a new Saved
-query: “`package:^chromeos`” named “chromeos”.
+You can use
+[Code Search](https://source.chromium.org/chromiumos/chromiumos/codesearch/)
+to lookup things in
+[Chromite](https://source.chromium.org/chromiumos/chromiumos/codesearch/+/HEAD:chromite/)
+or Chromium OS in general.
+
+Non-public code has a separate
+[internal Code Search site](https://source.corp.google.com/).
+It's organized into different ["repositories"](https://source.corp.google.com/repos),
+and we have two:
+["Chrome OS - Internal"](https://source.corp.google.com/chromeos_internal) (only
+internal repositories) &
+["Chrome OS - Public"](https://source.corp.google.com/chromeos_public) (only
+public repositories).
+You can add a search query for a single combined view (public & private) in the
+[Saved Queries settings page](https://source.corp.google.com/settings/savedqueries).
+Use the query `package:^chromeos_(internal|public)$`.
+NB: The "Chrome OS - Public" repository is exactly the same as the public
+source.chromium.org site.
 
 ### chromite/api
 
diff --git a/signing/README.md b/signing/README.md
index 8478166..3c9bff9 100644
--- a/signing/README.md
+++ b/signing/README.md
@@ -12,14 +12,6 @@
 [go/cros-domain-model](https://goto.corp.google.com/cros-domain-model) and are
 familiar with the contents.
 
-## Directory Overview
-
-You can use [Code Search](https://cs.corp.google.com/) to lookup things in
-Chromite or ChromeOS in general. You can add a ChromeOS filter to only show
-files from CrOS repositories by going to
-[CS Settings](https://cs.corp.google.com/settings/) and adding a new Saved
-query: “`package:^chromeos`” named “chromeos”.
-
 ### `signing/lib`
 
 Code here is expected to be imported whenever needed throughout