Missing changes for Cisco FTD (#13286) (#13379)

* Rename docs section to Field Mappings

* Add explanatory comment to the generator

filebeat/docs/modules/cisco.asciidoc

@@ -112,7 +112,7 @@ The Cisco FTD fileset primarily supports parsing IPv4 and IPv6 access list log
 messages similar to that of ASA devices as well as Security Event Syslog
 Messages for Intrusion, Connection, File and Malware events.
 
-*ECS Field mapping*
+*Field mappings*
 
 The `ftd` fileset maps Security Event Syslog Messages to the Elastic Common
 Schema (ECS) format. The following table illustrates the mapping from

x-pack/filebeat/module/cisco/_meta/docs.asciidoc

@@ -107,7 +107,7 @@ The Cisco FTD fileset primarily supports parsing IPv4 and IPv6 access list log
 messages similar to that of ASA devices as well as Security Event Syslog
 Messages for Intrusion, Connection, File and Malware events.
 
-*ECS Field mapping*
+*Field mappings*
 
 The `ftd` fileset maps Security Event Syslog Messages to the Elastic Common
 Schema (ECS) format. The following table illustrates the mapping from

x-pack/filebeat/module/cisco/shared/gen.go

@@ -4,5 +4,14 @@
 
 package shared
 
+// These generators will output the following files for the FTD:
+//  - ecs-mapping-processor.yml, an ingest pipeline processor that maps FTD
+//    security event fields to ECS.
+//  - ecs-mapping-docs.asciidoc, asciidoc tables to document those mappings.
+//
+// This files are not picked up by the FTD module. When generated, you need to
+// manually update the pipeline in ingest/asa-ftd-pipeline.yml
+// and the asciidoc tables into ../_meta/docs.asciidoc.
+
 //go:generate go run gen-ftd-ecs-mapping.go stringset.go -output ecs-mapping-processor.yml security-mappings.csv
 //go:generate go run gen-ecs-mapping-docs.go stringset.go -output ecs-mapping-docs.asciidoc security-mappings.csv