[PATCH docs] Add Gerrit server info to contributing doc

[OpenBMC Patches]

From: Adriana Kobylak <anoo at us.ibm.com>

Add steps to setup and push changes to the openbmc gerrit server.

Signed-off-by: Adriana Kobylak <anoo at us.ibm.com>
---
 contributing.md | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/contributing.md b/contributing.md
index db485a0..fb24acd 100644
--- a/contributing.md
+++ b/contributing.md
@@ -84,6 +84,36 @@ The guidelines in the Linux kernel are very useful:
 
 Your contribution will generally need to be reviewed before being accepted.
 
+
+Submitting changes via Gerrit server
+------------------------------------
+
+The openbmc gerrit server is https://gerrit.openbmc-project.xyz/#/q/status:open
+
+If you're going to be working with gerrit often, it's useful to create an SSH
+host block in ~/.ssh/config. Ex:
+```
+Host openbmc.gerrit
+        Hostname gerrit.openbmc-project.xyz
+        Port 29418
+        User your_github_id
+```
+
+From your openbmc git repository, add a remote to the gerrit server, where
+<openbmc_repo> is the current git repository you're working on, such as
+phosphor-rest-server:
+`remote add gerrit ssh://your_github_id@openbmc.gerrit/openbmc/openbmc_repo`
+
+Obtain the git hook commit-msg to automatically add a Change-Id to the commit
+message, which is needed by Gerrit:
+`gitdir=$(git rev-parse --git-dir)`
+`scp -p -P 29418 your_github_id at gerrit.openbmc-project.xyz:hooks/commit-msg ${gitdir}/hooks`
+
+To submit a change set, push to the gerrit server, where <gerrit> is the name
+of the remote added with the remote add command:
+`git push gerrit HEAD:refs/for/master`
+
+
 Avoid references to non-public resources
 ----------------------------------------
 
-- 
2.8.4