[doc] Update thread information in developer docs

Author: jnewbery

doc/developer-notes.md

@@ -423,27 +423,52 @@ and its `cs_KeyStore` lock for example).
 Threads
 -------
 
-- ThreadScriptCheck : Verifies block scripts.
+- [Main thread (`bitcoind`)](https://doxygen.bitcoincore.org/bitcoind_8cpp.html#a0ddf1224851353fc92bfbff6f499fa97)
+  : Started from `main()` in `bitcoind.cpp`. Responsible for starting up and
+  shutting down the application.
 
-- ThreadImport : Loads blocks from `blk*.dat` files or `-loadblock=<file>`.
+- [ThreadImport (`b-loadblk`)](https://doxygen.bitcoincore.org/init_8cpp.html#ae9e290a0e829ec0198518de2eda579d1)
+  : Loads blocks from `blk*.dat` files or `-loadblock=<file>` on startup.
 
-- ThreadDNSAddressSeed : Loads addresses of peers from the DNS.
+- [ThreadScriptCheck (`b-scriptch.x`)](https://doxygen.bitcoincore.org/validation_8cpp.html#a925a33e7952a157922b0bbb8dab29a20)
+  : Parallel script validation threads for transactions in blocks.
 
-- ThreadMapPort : Universal plug-and-play startup/shutdown.
+- [ThreadHTTP (`b-http`)](https://doxygen.bitcoincore.org/httpserver_8cpp.html#abb9f6ea8819672bd9a62d3695070709c)
+  : Libevent thread to listen for RPC and REST connections.
 
-- ThreadSocketHandler : Sends/Receives data from peers on port 8333.
+- [HTTP worker threads(`b-httpworker.x`)](https://doxygen.bitcoincore.org/httpserver_8cpp.html#aa6a7bc27265043bc0193220c5ae3a55f)
+  : Threads to service RPC and REST requests.
 
-- ThreadOpenAddedConnections : Opens network connections to added nodes.
+- [Indexer threads (`b-txindex`, etc)](https://doxygen.bitcoincore.org/class_base_index.html#a96a7407421fbf877509248bbe64f8d87)
+  : One thread per indexer.
 
-- ThreadOpenConnections : Initiates new connections to peers.
+- [SchedulerThread (`b-scheduler`)](https://doxygen.bitcoincore.org/class_c_scheduler.html#a14d2800815da93577858ea078aed1fba)
+  : Does asynchronous background tasks like dumping wallet contents, dumping
+  addrman and running asynchronous validationinterface callbacks.
 
-- ThreadMessageHandler : Higher-level message handling (sending and receiving).
+- [TorControlThread (`b-torcontrol`)](https://doxygen.bitcoincore.org/torcontrol_8cpp.html#a4faed3692d57a0d7bdbecf3b37f72de0)
+  : Libevent thread for tor connections.
 
-- DumpAddresses : Dumps IP addresses of nodes to `peers.dat`.
+- Net threads:
 
-- ThreadRPCServer : Remote procedure call handler, listens on port 8332 for connections and services them.
+  - [ThreadMessageHandler (`b-msghand`)](https://doxygen.bitcoincore.org/class_c_connman.html#aacdbb7148575a31bb33bc345e2bf22a9)
+    : Application level message handling (sending and receiving). Almost
+    all net_processing and validation logic runs on this thread.
 
-- Shutdown : Does an orderly shutdown of everything.
+  - [ThreadDNSAddressSeed (`b-dnsseed`)](https://doxygen.bitcoincore.org/class_c_connman.html#aa7c6970ed98a4a7bafbc071d24897d13)
+    : Loads addresses of peers from the DNS.
+
+  - [ThreadMapPort (`b-upnp`)](https://doxygen.bitcoincore.org/net_8cpp.html#a63f82a71c4169290c2db1651a9bbe249)
+    : Universal plug-and-play startup/shutdown.
+
+  - [ThreadSocketHandler (`b-net`)](https://doxygen.bitcoincore.org/class_c_connman.html#a765597cbfe99c083d8fa3d61bb464e34)
+    : Sends/Receives data from peers on port 8333.
+
+  - [ThreadOpenAddedConnections (`b-addcon`)](https://doxygen.bitcoincore.org/class_c_connman.html#a0b787caf95e52a346a2b31a580d60a62)
+    : Opens network connections to added nodes.
+
+  - [ThreadOpenConnections (`b-opencon`)](https://doxygen.bitcoincore.org/class_c_connman.html#a55e9feafc3bab78e5c9d408c207faa45)
+    : Initiates new connections to peers.
 
 Ignoring IDE/editor files
 --------------------------