Add comment explaining early guard

esphome/components/seeed_mr24hpc1/seeed_mr24hpc1.cpp

@@ -106,6 +106,8 @@ void MR24HPC1Component::update_() {
 
 // main loop
 void MR24HPC1Component::loop() {
+  // Early return avoids stack adjustment for the batch buffer below.
+  // loop() runs ~7000/min so most calls have nothing to read.
   int avail = this->available();
   if (avail > 0) {
     // Read all available bytes in batches to reduce UART call overhead.

esphome/components/seeed_mr60bha2/seeed_mr60bha2.cpp

@@ -30,6 +30,8 @@ void MR60BHA2Component::dump_config() {
 
 // main loop
 void MR60BHA2Component::loop() {
+  // Early return avoids stack adjustment for the batch buffer below.
+  // loop() runs ~7000/min so most calls have nothing to read.
   int avail = this->available();
   if (avail <= 0) {
     return;

esphome/components/seeed_mr60fda2/seeed_mr60fda2.cpp

@@ -49,6 +49,8 @@ void MR60FDA2Component::setup() {
 
 // main loop
 void MR60FDA2Component::loop() {
+  // Early return avoids stack adjustment for the batch buffer below.
+  // loop() runs ~7000/min so most calls have nothing to read.
   int avail = this->available();
   if (avail <= 0) {
     return;