doc: announce ethdev functions will not return void

void return value is bad for get API (like rte_eth_dev_info-get())
since caller does not know if the function does its job or not and
output value is filled in.

void return value is bad for state changing API (like
rte_eth_promiscuous_enable()) since caller should use get API
to understand if state is really changed.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Jerin Jacob <jerinj@marvell.com>

doc/guides/rel_notes/deprecation.rst

@@ -79,6 +79,20 @@ Deprecation Notices
   Target release for removal of the legacy API will be defined once most
   PMDs have switched to rte_flow.
 
+* ethdev: Update API functions returning ``void`` to return ``int`` with
+  negative errno values to indicate various error conditions (e.g.
+  invalid port ID, unsupported operation, failed operation):
+
+  - ``rte_eth_dev_info_get``
+  - ``rte_eth_promiscuous_enable`` and ``rte_eth_promiscuous_disable``
+  - ``rte_eth_allmulticast_enable`` and ``rte_eth_allmulticast_disable``
+  - ``rte_eth_link_get`` and ``rte_eth_link_get_nowait``
+  - ``rte_eth_dev_stop``
+  - ``rte_eth_dev_close``
+  - ``rte_eth_xstats_reset``
+  - ``rte_eth_macaddr_get``
+  - ``rte_eth_dev_owner_delete``
+
 * cryptodev: support for using IV with all sizes is added, J0 still can
   be used but only when IV length in following structs ``rte_crypto_auth_xform``,
   ``rte_crypto_aead_xform`` is set to zero. When IV length is greater or equal