net: dsa: add NETC switch tag support

The NXP NETC switch tag is a proprietary header added to frames after the
source MAC address. The switch tag has 3 types, and each type has 1 ~ 4
subtypes, the details are as follows.

Forward NXP switch tag (Type=0): Represents forwarded frames.
  - SubType = 0 - Normal frame processing.

To_Port NXP switch tag (Type=1): Represents frames that are to be sent
to a specific switch port.
  - SubType = 0. No request to perform timestamping.
  - SubType = 1. Request to perform one-step timestamping.
  - SubType = 2. Request to perform two-step timestamping.
  - SubType = 3. Request to perform both one-step timestamping and
    two-step timestamping.

To_Host NXP switch tag (Type=2): Represents frames redirected or copied
to the switch management port.
  - SubType = 0. Received frames redirected or copied to the switch
    management port.
  - SubType = 1. Received frames redirected or copied to the switch
    management port with captured timestamp at the switch port where
    the frame was received.
  - SubType = 2. Transmit timestamp response (two-step timestamping).

In addition, the length of different type switch tag is different, the
minimum length is 6 bytes, the maximum length is 14 bytes. Currently,
Forward tag, SubType 0 of To_Port tag and Subtype 0 of To_Host tag are
supported. More tags will be supported in the future.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Link: https://patch.msgid.link/20260518082506.1318236-10-wei.fang@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

3 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/dsa/tag_netc.h b/include/linux/dsa/tag_netc.h
new file mode 100644
index 000000000000..fe964722e5b0
--- /dev/null
+++ b/include/linux/dsa/tag_netc.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright 2025-2026 NXP
+ */
+
+#ifndef __NET_DSA_TAG_NETC_H
+#define __NET_DSA_TAG_NETC_H
+
+#include <linux/skbuff.h>
+#include <net/dsa.h>
+
+#define NETC_TAG_MAX_LEN			14
+
+#endif
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 4cc67469cf2e..8c16ef23cc10 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -58,6 +58,7 @@ struct tc_action;
 #define DSA_TAG_PROTO_YT921X_VALUE		30
 #define DSA_TAG_PROTO_MXL_GSW1XX_VALUE		31
 #define DSA_TAG_PROTO_MXL862_VALUE		32
+#define DSA_TAG_PROTO_NETC_VALUE		33
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -93,6 +94,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_YT921X		= DSA_TAG_PROTO_YT921X_VALUE,
 	DSA_TAG_PROTO_MXL_GSW1XX	= DSA_TAG_PROTO_MXL_GSW1XX_VALUE,
 	DSA_TAG_PROTO_MXL862		= DSA_TAG_PROTO_MXL862_VALUE,
+	DSA_TAG_PROTO_NETC		= DSA_TAG_PROTO_NETC_VALUE,
 };
 
 struct dsa_switch;
diff --git a/include/uapi/linux/if_ether.h b/include/uapi/linux/if_ether.h
index df9d44a11540..fb5efc8e06cc 100644
--- a/include/uapi/linux/if_ether.h
+++ b/include/uapi/linux/if_ether.h
@@ -123,6 +123,7 @@
 #define ETH_P_DSA_A5PSW	0xE001		/* A5PSW Tag Value [ NOT AN OFFICIALLY REGISTERED ID ] */
 #define ETH_P_IFE	0xED3E		/* ForCES inter-FE LFB type */
 #define ETH_P_AF_IUCV   0xFBFB		/* IBM af_iucv [ NOT AN OFFICIALLY REGISTERED ID ] */
+#define ETH_P_NXP_NETC  0xFD3A		/* NXP NETC DSA [ NOT AN OFFICIALLY REGISTERED ID ] */
 
 #define ETH_P_802_3_MIN	0x0600		/* If the value in the ethernet type is more than this value
 					 * then the frame is Ethernet II. Else it is 802.3 */