Improved some docstrings for grpc_call creation

include/grpc/grpc.h

@@ -170,8 +170,9 @@ GRPCAPI void grpc_channel_watch_connectivity_state(
     completions are sent to 'completion_queue'. 'method' and 'host' need only
     live through the invocation of this function.
     If parent_call is non-NULL, it must be a server-side call. It will be used
-    to propagate properties from the server call to this new client call.
-    */
+    to propagate properties from the server call to this new client call,
+    depending on the value of \a propagation_mask (see propagation_bits.h for
+    possible values). */
 GRPCAPI grpc_call *grpc_channel_create_call(
     grpc_channel *channel, grpc_call *parent_call, uint32_t propagation_mask,
     grpc_completion_queue *completion_queue, const char *method,
@@ -187,7 +188,8 @@ GRPCAPI void *grpc_channel_register_call(grpc_channel *channel,
                                          const char *method, const char *host,
                                          void *reserved);
 
-/** Create a call given a handle returned from grpc_channel_register_call */
+/** Create a call given a handle returned from grpc_channel_register_call.
+    \sa grpc_channel_create_call. */
 GRPCAPI grpc_call *grpc_channel_create_registered_call(
     grpc_channel *channel, grpc_call *parent_call, uint32_t propagation_mask,
     grpc_completion_queue *completion_queue, void *registered_call_handle,

src/core/ext/lb_policy/grpclb/grpclb.c

@@ -767,6 +767,9 @@ static lb_client_data *lb_client_data_create(glb_lb_policy *glb_policy) {
   lb_client->deadline = gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC),
                                      gpr_time_from_seconds(3, GPR_TIMESPAN));
 
+  /* Note the following LB call progresses every time there's activity in \a
+   * glb_policy->base.interested_parties, which is comprised of the polling
+   * entities passed to glb_pick(). */
   lb_client->lb_call = grpc_channel_create_pollset_set_call(
       glb_policy->lb_channel, NULL, GRPC_PROPAGATE_DEFAULTS,
       glb_policy->base.interested_parties, "/BalanceLoad",

src/core/lib/surface/channel.h

@@ -42,6 +42,14 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
                                   grpc_channel_stack_type channel_stack_type,
                                   grpc_transport *optional_transport);
 
+/** Create a call given a grpc_channel, in order to call \a method.
+    Progress is tied to activity on \a pollset_set. The returned call object is
+    meant to be used with \a grpc_call_start_batch_and_execute, which relies on
+    callbacks to signal completions. \a method and \a host need
+    only live through the invocation of this function. If \a parent_call is
+    non-NULL, it must be a server-side call. It will be used to propagate
+    properties from the server call to this new client call, depending on the
+    value of \a propagation_mask (see propagation_bits.h for possible values) */
 grpc_call *grpc_channel_create_pollset_set_call(
     grpc_channel *channel, grpc_call *parent_call, uint32_t propagation_mask,
     grpc_pollset_set *pollset_set, const char *method, const char *host,