ethtool: add FEC bins histogram report

IEEE 802.3ck-2022 defines counters for FEC bins and 802.3df-2024
clarifies it a bit further. Implement reporting interface through as
addition to FEC stats available in ethtool. Drivers can leave bin
counter uninitialized if per-lane values are provided. In this case the
core will recalculate summ for the bin.

Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Link: https://patch.msgid.link/20250924124037.1508846-2-vadim.fedorenko@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/ethtool.yaml

@@ -1219,6 +1219,30 @@ attribute-sets:
         name: udp-ports
         type: nest
         nested-attributes: tunnel-udp
+  -
+    name: fec-hist
+    attr-cnt-name: --ethtool-a-fec-hist-cnt
+    attributes:
+      -
+        name: pad
+        type: pad
+      -
+        name: bin-low
+        type: u32
+        doc: Low bound of FEC bin (inclusive)
+      -
+        name: bin-high
+        type: u32
+        doc: High bound of FEC bin (inclusive)
+      -
+        name: bin-val
+        type: uint
+        doc: Error count in the bin (optional if per-lane values exist)
+      -
+        name: bin-val-per-lane
+        type: binary
+        sub-type: u64
+        doc: An array of per-lane error counters in the bin (optional)
   -
     name: fec-stat
     attr-cnt-name: __ethtool-a-fec-stat-cnt
@@ -1242,6 +1266,11 @@ attribute-sets:
         name: corr-bits
         type: binary
         sub-type: u64
+      -
+        name: hist
+        type: nest
+        multi-attr: True
+        nested-attributes: fec-hist
   -
     name: fec
     attr-cnt-name: __ethtool-a-fec-cnt