Support for LibreTiny platform (RTL8710, BK7231 & other modules) (#3509)

Co-authored-by: Kuba Szczodrzyński <kuba@szczodrzynski.pl>
Co-authored-by: Sam Neirinck <git@samneirinck.com>
Co-authored-by: David Buezas <dbuezas@users.noreply.github.com>
Co-authored-by: Stroe Andrei Catalin <catalin2402@gmail.com>
Co-authored-by: Sam Neirinck <github@samneirinck.be>
Co-authored-by: Péter Sárközi <xmisterhu@gmail.com>
Co-authored-by: Hajo Noerenberg <hn@users.noreply.github.com>

platformio.ini

@@ -4,7 +4,7 @@
 ; It's *not* used during runtime.
 
 [platformio]
-default_envs = esp8266-arduino, esp32-arduino, esp32-idf
+default_envs = esp8266-arduino, esp32-arduino, esp32-idf, bk72xx-arduino
 ; Ideally, we want src_dir to be the root directory of the repository, to mimic the runtime build
 ; environment as best as possible. Unfortunately, the ESP-IDF toolchain really doesn't like this
 ; being the root directory. Instead, set esphome/ as the source directory, all our sources are in
@@ -167,6 +167,16 @@ build_flags =
     -DUSE_RP2040
     -DUSE_RP2040_FRAMEWORK_ARDUINO
 
+; This are common settings for the LibreTiny (all variants) using Arduino.
+[common:libretiny-arduino]
+extends = common:arduino
+platform = libretiny
+framework = arduino
+build_flags =
+    ${common:arduino.build_flags}
+    -DUSE_LIBRETINY
+build_src_flags = -include Arduino.h
+
 ; All the actual environments are defined below.
 
 ;;;;;;;; ESP8266 ;;;;;;;;
@@ -339,6 +349,35 @@ build_flags =
     ${common:rp2040-arduino.build_flags}
     ${flags:runtime.build_flags}
 
+;;;;;;;; LibreTiny ;;;;;;;;
+
+[env:bk72xx-arduino]
+extends = common:libretiny-arduino
+board = generic-bk7231n-qfn32-tuya
+build_flags =
+    ${common:libretiny-arduino.build_flags}
+    ${flags:runtime.build_flags}
+    -DUSE_BK72XX
+    -DUSE_LIBRETINY_VARIANT_BK7231N
+
+[env:rtl87xxb-arduino]
+extends = common:libretiny-arduino
+board = generic-rtl8710bn-2mb-788k
+build_flags =
+    ${common:libretiny-arduino.build_flags}
+    ${flags:runtime.build_flags}
+    -DUSE_RTL87XX
+    -DUSE_LIBRETINY_VARIANT_RTL8710B
+
+[env:rtl87xxc-arduino]
+extends = common:libretiny-arduino
+board = generic-rtl8720cf-2mb-992k
+build_flags =
+    ${common:libretiny-arduino.build_flags}
+    ${flags:runtime.build_flags}
+    -DUSE_RTL87XX
+    -DUSE_LIBRETINY_VARIANT_RTL8720C
+
 [env:host]
 extends = common
 platform = platformio/native