net: dsa: add Broadcom tag RX/TX handler

Add support for the 4-bytes Broadcom tag that built-in switches such as
the Starfighter 2 might insert when receiving packets, or that we need
to insert while targetting specific switch ports. We use a fake local
EtherType value for this 4-bytes switch tag: ETH_P_BRCMTAG to make sure
we can assign DSA-specific network operations within the DSA drivers.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 2c9563f..9771292 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -19,6 +19,11 @@
 #include <linux/phy.h>
 #include <linux/phy_fixed.h>
 
+/* Not an official ethertype value, used only internally for DSA
+ * demultiplexing
+ */
+#define ETH_P_BRCMTAG		(ETH_P_XDSA + 1)
+
 #define DSA_MAX_SWITCHES	4
 #define DSA_MAX_PORTS		12