Add hints about secure delegation to DNSSEC chapter of the ARM

Let's not duplicate texts from elsewhere, just point to different parts
of documentation.

doc/arm/dnssec.inc.rst

@@ -77,6 +77,7 @@ These filenames contain:
    safe location and protect them from unauthorized access. Anyone with
    access to the private key can create fake but seemingly valid DNS data.
 
+
 .. _dnssec_kasp:
 
 Fully Automated (Key and Signing Policy)
@@ -428,6 +429,44 @@ to provide the parent zone administrators with the ``DNSKEYs`` (or their
 corresponding ``DS`` records) that are the secure entry point to the zone.
 
 
+.. _secure_delegation:
+
+Secure Delegation
+~~~~~~~~~~~~~~~~~
+
+Once a zone is signed on the authoritative servers, the last remaining step
+is to establish chain of trust [#validation]_ between the parent zone
+(``example.``) and the local zone (``dnssec.example.``).
+
+Generally the procedure is:
+
+  - **Wait** for stale data to expire from caches. The amount of time required
+    is equal to the maximum TTL value used in the zone before signing. This
+    step ensures that unsigned data expire from caches and resolvers do not get
+    confused by missing signatures.
+  - Insert/update DS records in the parent zone (``dnssec.example. DS`` record).
+
+There are multiple ways to update DS records in the parent zone. Refer to the
+documentation for the parent zone to find out which options are applicable to
+a given case zone. Generally the options are, from most- to least-recommended:
+
+  - Automatically update the DS record in the parent zone using
+    ``CDS``/``CDNSKEY`` records automatically generated by BIND. This requires
+    support for :rfc:`7344` in either parent zone, registry, or registrar. In
+    that case, configure BIND to :ref:`monitor DS records in the parent
+    zone <cds_cdnskey>` and everything will happen automatically at the right
+    time.
+  - Query the zone for automatically generated ``CDS`` or ``CDNSKEY`` records using
+    :iscman:`dig`, and then insert these records into the parent zone using
+    the method specified by the parent zone (web form, e-mail, API, ...).
+  - Generate DS records manually using the :iscman:`dnssec-dsfromkey` utility on
+    `zone keys`_, and then insert them into the parent zone.
+
+.. [#validation] For further details on how the chain of trust is used in practice, see
+                :ref:`dnssec_12_steps` in the :doc:`dnssec-guide`.
+
+
+
 DNSSEC Validation
 ~~~~~~~~~~~~~~~~~