kernel: Add KERNEL_DCB (Data Center Bridging)

The kmod-mlxsw-spectrum driver activated CONFIG_DCB indirectly already
on all targets which are building this driver. All other DCB capable
driver did not activate their DCB support.

CONFIG_DCB increases the uncompressed kernel size by about 7.8KB.

CONFIG_DCB is only needed some data center Ethernet cards and not used
on normal routers. Activate it only on the x86_64 and the armsr_arm64
target which are used on normal servers or in VMs.

Link: https://github.com/openwrt/openwrt/pull/17672
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

config/Config-kernel.in

@@ -1212,6 +1212,28 @@ config KERNEL_NET_L3_MASTER_DEV
 	  drivers to support L3 master devices like VRF.
   	  Increases the compressed kernel size by ~4kB (as of Linux 6.6).
 
+config KERNEL_DCB
+	bool "Data Center Bridging support"
+	default y if TARGET_armsr_armv8
+	default y if TARGET_x86_64
+	help
+	  This enables support for configuring Data Center Bridging (DCB)
+	  features on DCB capable Ethernet adapters via rtnetlink.  Say 'Y'
+	  if you have a DCB capable Ethernet adapter which supports this
+	  interface and you are connected to a DCB capable switch.
+
+	  DCB is a collection of Ethernet enhancements which allow DCB capable
+	  NICs and switches to support network traffic with differing
+	  requirements (highly reliable, no drops vs. best effort vs. low
+	  latency) to co-exist on Ethernet.
+
+	  DCB features include:
+	    Enhanced Transmission Selection (aka Priority Grouping) - provides a
+	      framework for assigning bandwidth guarantees to traffic classes.
+	    Priority-based Flow Control (PFC) - a MAC control pause frame which
+	      works at the granularity of the 802.1p priority instead of the
+	      link (802.3x).
+
 config KERNEL_XDP_SOCKETS
 	bool "XDP sockets support"
 	help