docs: ethtool: document ETHTOOL_A_STATS_SRC and ETHTOOL_A_PAUSE_STATS_SRC

Two new netlink attributes were added to PAUSE_GET and STATS_GET and
their replies. Document them.
Signed-off-by: NVladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/ethtool-netlink.rst

@@ -1092,8 +1092,18 @@ Request contents:
 
   =====================================  ======  ==========================
   ``ETHTOOL_A_PAUSE_HEADER``             nested  request header
+  ``ETHTOOL_A_PAUSE_STATS_SRC``          u32     source of statistics
   =====================================  ======  ==========================
 
+``ETHTOOL_A_PAUSE_STATS_SRC`` is optional. It takes values from:
+
+.. kernel-doc:: include/uapi/linux/ethtool.h
+    :identifiers: ethtool_mac_stats_src
+
+If absent from the request, stats will be provided with
+an ``ETHTOOL_A_PAUSE_STATS_SRC`` attribute in the response equal to
+``ETHTOOL_MAC_STATS_SRC_AGGREGATE``.
+
 Kernel response contents:
 
   =====================================  ======  ==========================
@@ -1508,6 +1518,7 @@ Request contents:
 
   =======================================  ======  ==========================
   ``ETHTOOL_A_STATS_HEADER``               nested  request header
+  ``ETHTOOL_A_STATS_SRC``                  u32     source of statistics
   ``ETHTOOL_A_STATS_GROUPS``               bitset  requested groups of stats
   =======================================  ======  ==========================
 
@@ -1516,6 +1527,8 @@ Kernel response contents:
  +-----------------------------------+--------+--------------------------------+
  | ``ETHTOOL_A_STATS_HEADER``        | nested | reply header                   |
  +-----------------------------------+--------+--------------------------------+
+ | ``ETHTOOL_A_STATS_SRC``           | u32    | source of statistics           |
+ +-----------------------------------+--------+--------------------------------+
  | ``ETHTOOL_A_STATS_GRP``           | nested | one or more group of stats     |
  +-+---------------------------------+--------+--------------------------------+
  | | ``ETHTOOL_A_STATS_GRP_ID``      | u32    | group ID - ``ETHTOOL_STATS_*`` |
@@ -1577,6 +1590,11 @@ Low and high bounds are inclusive, for example:
  etherStatsPkts512to1023Octets 512  1023
  ============================= ==== ====
 
+``ETHTOOL_A_STATS_SRC`` is optional. Similar to ``PAUSE_GET``, it takes values
+from ``enum ethtool_mac_stats_src``. If absent from the request, stats will be
+provided with an ``ETHTOOL_A_STATS_SRC`` attribute in the response equal to
+``ETHTOOL_MAC_STATS_SRC_AGGREGATE``.
+
 PHC_VCLOCKS_GET
 ===============