commit ab77c5b176750f243f36c2ce6f334712658c85fc
Author: Zane Bitter <zbitter@redhat.com>
Date:   Thu Oct 15 14:51:04 2020 -0400

    Document by_path root device hint
    
    Support for this was added in https://review.opendev.org/500524 but
    never documented.
    
    Change-Id: Icc67ea11bd3dde08bfdc1e46d8c32d425f9ae4ac

diff --git a/doc/source/install/include/root-device-hints.inc b/doc/source/install/include/root-device-hints.inc
index 51452be..e31bd22 100644
--- a/doc/source/install/include/root-device-hints.inc
+++ b/doc/source/install/include/root-device-hints.inc
@@ -26,6 +26,8 @@ which disk it should pick for the deployment. The list of supported hints is:
   rotational) when choosing which disk Ironic should deploy the image onto.
 * hctl (STRING): the SCSI address (Host, Channel, Target and Lun),
   e.g '1:0:0:0'
+* by_path (STRING): the alternate device name corresponding to a particular
+  PCI or iSCSI path, e.g /dev/disk/by-path/pci-0000:00
 * name (STRING): the device name, e.g /dev/md0