doc/cephadm: link to "host pattern" matching sect

Link to the "Placement by Pattern Matching" section in
doc/cephadm/services/index.rst from the "Advanced OSD Service
Specifications" section in doc/cephadm/services/osd.rst.

Fixes: https://tracker.ceph.com/issues/68812

Signed-off-by: Zac Dover <[email protected]>

Author: zdover23

doc/cephadm/services/index.rst

@@ -357,6 +357,8 @@ Or in YAML:
 
 * See :ref:`orchestrator-host-labels`
 
+.. _cephadm-services-placement-by-pattern-matching:
+
 Placement by pattern matching
 -----------------------------
 

doc/cephadm/services/osd.rst

@@ -520,8 +520,9 @@ This means :
 
 #. Turn any available device (ceph-volume decides what 'available' is) into an
    OSD on all hosts that match the glob pattern '*'. (The glob pattern matches
-   against the registered hosts from `host ls`) A more detailed section on
-   host_pattern is available below.
+   against the registered hosts from `host ls`) See
+   :ref:`cephadm-services-placement-by-pattern-matching` for more on using
+   ``host_pattern``-matching to turn devices into OSDs.
 
 #. Then pass it to `osd create` like this: