net/smc: Add documentation for limit_smc_hs and hs_ctrl

Document missing SMC sysctl parameters limit_smc_hs and hs_ctrl

Signed-off-by: Kyoji Ogasawara <sawara04.o@gmail.com>
Reviewed-by: D. Wythe<alibuda@linux.alibaba.com>
Link: https://patch.msgid.link/20260309124541.22723-3-sawara04.o@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/smc-sysctl.rst

@@ -111,3 +111,30 @@ smcr_max_recv_wr - INTEGER
 	like before having this control.
 
 	Default: 48
+
+limit_smc_hs - INTEGER
+	Whether to limit SMC handshake for newly created sockets.
+
+	When enabled, SMC listen path applies handshake limitation based on
+	handshake worker congestion and queued SMC handshake load.
+
+	Possible values:
+
+	- 0 - Disable handshake limitation
+	- 1 - Enable handshake limitation
+
+	Default: 0 (disable)
+
+hs_ctrl - STRING
+	Select the SMC handshake control profile by name.
+
+	This string refers to the name of a user-implemented
+	BPF struct_ops instance of type smc_hs_ctrl.
+
+	The selected profile controls whether SMC options are advertised
+	during TCP SYN/SYN-ACK handshake.
+
+	Only available when CONFIG_SMC_HS_CTRL_BPF is enabled.
+	Write an empty string to clear the current profile.
+
+	Default: empty string