Tools: added more bootloader details

Tools/bootloaders/README.txt

@@ -2,8 +2,47 @@ These FMU and FMUv2 bootloader images are built from:
 
   https://github.com/ArduPilot/Bootloader
 
-On PX4 builds they are in ROMFS to make it easier for users to update
+Bootloader details
-their bootloaders using:
+------------------
+
+px4fmu_bl.bin:
+   for F405 based fmuv1
+   boots at 0x08004000
+   board ID 5
+
+px4fmuv2_bl.bin:
+   for F427 based fmuv2 boards
+   boots at 0x08004000
+   board ID 9
+
+px4fmuv4_bl.bin:
+   for F427 based fmuv4 boards
+   boots at 0x08004000
+   board ID 11
+
+px4io_bl.bin:
+   for IOMCU on fmuv1
+
+revo405_bl.bin:
+   for F405 based revolution boards
+   boots at 0x08010000
+   reserve sector at 0x08004000 for OSD storage
+   reserves sectors at 0x08008000 and 0x0800C000 for ArduPilot storage
+   board ID 70
+
+px4fmuv4pro_bl.bin:
+   for F427 based p4pro board from drotek
+
+skyviper_v2450_bl.bin:
+   for F427 based skyviper-v2450 boards (based on fmuv3)
+   reserves sectors 22 and 23 for ArduPilot storage
+   board ID 9
+
+Bootloader update on px4 builds
+-------------------------------
+
+For ArduPilot builds using HAL_PX4 the bootloaders are stored in ROMFS
+to make it easier for users to update their bootloaders using:
 
  bl_update /etc/bootloader/fmu_bl.bin
 
@@ -12,4 +51,3 @@ test -> shell, or by booting with no SD card installed
 
 to use NSH to do this, please see the Wiki
 http://dev.ardupilot.org/wiki/interfacing-with-pixhawk-using-the-nsh
-