RDMA/ib_srp: Add more documentation

Make it more clear what the different ib_srp data structures represent.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bart Van Assche <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/ulp/srp/ib_srp.h

···
 };
 
 /*
+ * RDMA adapter in the initiator system.
+ *
+ * @dev_list: List of RDMA ports associated with this RDMA adapter (srp_host).
  * @mr_page_mask: HCA memory registration page mask.
  * @mr_page_size: HCA memory registration page size.
  * @mr_max_size: Maximum size in bytes of a single FR registration request.
···
 	bool			use_fast_reg;
 };
 
+/*
+ * One port of an RDMA adapter in the initiator system.
+ *
+ * @target_list: List of connected target ports (struct srp_target_port).
+ * @target_lock: Protects @target_list.
+ */
 struct srp_host {
 	struct srp_device      *srp_dev;
 	u8			port;
···
 };
 
 /**
- * struct srp_target_port
+ * struct srp_target_port - RDMA port in the SRP target system
  * @comp_vector: Completion vector used by the first RDMA channel created for
  *   this target port.
  */